Calendar date
Encyclopedia
A date in a calendar is a reference to a particular day represented within a calendar
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
, with era
referring to the particular period of time (Note the different use
of the terms in geology
).
The most widely used epoch is a conventional
birthdate of Jesus (which was established by Dionysius Exiguus
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Examples for the 9th of November 2003:
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
and The Times
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
considers its ISO 8601
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
s, spreadsheet
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
. Some U.S. government agencies now use ISO 8601
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
.
standard
date format is that the lexicographical order
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
, this format is usually referred to as "ordinal date
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
or its successor, z/OS
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
A date in a calendar is a reference to a particular day represented within a calendar
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
, with era
referring to the particular period of time (Note the different use
of the terms in geology
).
The most widely used epoch is a conventional
birthdate of Jesus (which was established by Dionysius Exiguus
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endianness
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Examples for the 9th of November 2003:
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
and The Times
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
considers its ISO 8601
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
s, spreadsheet
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
. Some U.S. government agencies now use ISO 8601
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
.
standard
date format is that the lexicographical order
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
, this format is usually referred to as "ordinal date
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
or its successor, z/OS
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
A date in a calendar is a reference to a particular day represented within a calendar
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
, with era
referring to the particular period of time (Note the different use
of the terms in geology
).
The most widely used epoch is a conventional
birthdate of Jesus (which was established by Dionysius Exiguus
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endianness
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Examples for the 9th of November 2003:
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
and The Times
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
considers its ISO 8601
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
s, spreadsheet
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
. Some U.S. government agencies now use ISO 8601
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
.
standard
date format is that the lexicographical order
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
, this format is usually referred to as "ordinal date
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
or its successor, z/OS
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
Calendar
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
Japan Standard Time
Japan Standard Time or JST is the standard timezone of Japan, and is 9 hours ahead of UTC. For example, when it is midnight in UTC, it is 09:00 in Japan Standard Time. There is no daylight saving time, though its introduction has been debated several times. Japan Standard Time is the same as...
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...
, with era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...
referring to the particular period of time (Note the different use
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
of the terms in geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
).
The most widely used epoch is a conventional
Convention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
birthdate of Jesus (which was established by Dionysius Exiguus
Dionysius Exiguus
Dionysius Exiguus was a 6th-century monk born in Scythia Minor, modern Dobruja shared by Romania and Bulgaria. He was a member of the Scythian monks community concentrated in Tomis, the major city of Scythia Minor...
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
Date format
Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endiannessEndianness
In computing, the term endian or endianness refers to the ordering of individually addressable sub-components within the representation of a larger data item as stored in external memory . Each sub-component in the representation has a unique degree of significance, like the place value of digits...
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Little endian forms, starting with the day
This sequence is common to the vast majority of the world's countries. This date format originates from the custom of writing the date as 'the 9th day of November in the year of our Lord 2003' in western religious and legal documents, which at one time were the majority of documents created. The format has shortened over time but the order of the elements has remained constant.- "9 November 2003" or "9. November 2003" (the latter is common in German-speaking regions)
- 9/11/2003 or 9.11.2003
- 09-Nov-2003 (used in the USA)
- 9-11-2003 (used in IrelandIrelandIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and the United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and is accepted in South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
& New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
) - [The] 9th [of] November 2003 (The 'of' and 'the' may be included in speech; they are omitted in all but the most formal writing.)
- Sunday, 9 November 2003
- 9/xi/03, 9.xi.03, 9-xi.03, or 9.XI.2003 (using the Roman numeralRoman numeralsThe numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
for the month) – This is usually confined to handwriting only and is not put into any form of print. It is associated with a number of schools and universities. It has also been used by the Vatican as an alternative to using months named after Roman deities. - 9 November ADAnno Dominiand Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....
2003
Big endian forms, starting with the year
In this format the most significant data item is written before lesser data items i.e. year before month before day. It is consistent with the big endianness of the Indian decimal numbering system, which progresses from the highest to the lowest order magnitude. That is, using this format textual orderings and chronological orderings are identical. This form is standard in Asian countries, Hungary, Sweden and the US armed forces.Examples for the 9th of November 2003:
- 2003-11-09: the ISO 8601ISO 8601ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
international standardInternational standardInternational standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...
orders the components of a date like this, and additionally uses leading zeros, for example, 0813-03-01, to be easily read and sorted by computers. It is used with UTC in the Internet date/time format (see the external link below). This format is also favoured in certain AsiaAsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
n countries, mainly East Asian countries, as well as in some European countries. The big endian convention is also frequently used in CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, but all three conventions are used there. - 2003 November 9
- 2003Nov9
- 2003Nov09
- 2003-Nov-9
- 2003-Nov-09
- 2003-Nov-9, Sunday
- 2003. 9. – The official format in HungaryHungaryHungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, point after year and day, month name with small initial. Following shorter formats also can be used: 2003. . 9., 2003. 11. 9., 2003. XI. 9. - 2003.11.9 using dots and no leading zeros, common in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
Middle endian forms, starting with the month
This sequence is used primarily in the United States, partially in Canada, and a few other countries . This date format was commonly used alongside the small endian form in the United Kingdom until the early 20th Century, and can be found in both defunct and modern print media such as the London GazetteLondon Gazette
The London Gazette is one of the official journals of record of the British government, and the most important among such official journals in the United Kingdom, in which certain statutory notices are required to be published...
and The Times
The Times
The Times is a British daily national newspaper, first published in London in 1785 under the title The Daily Universal Register . The Times and its sister paper The Sunday Times are published by Times Newspapers Limited, a subsidiary since 1981 of News International...
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
- Sunday, November 9, 2003
- November 9, 2003
- Nov. 9, 2003 or 11/9/2003
- 11-9-2003, 11.9.2003, 11.09.03, or 11/09/03
Usage issues
The many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits.For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
considers its ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
s, spreadsheet
Spreadsheet
A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
Federal Information Processing Standard
A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
Year 2000 problem
The Year 2000 problem was a problem for both digital and non-digital documentation and data storage situations which resulted from the practice of abbreviating a four-digit year to two digits.In computer programs, the practice of representing the year with two...
. Some U.S. government agencies now use ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
Old Style and New Style dates
Old Style and New Style are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January even though documents written at the time use a different start of year ; or to indicate that a date conforms to the Julian...
.
World locations by date format in use
Advantages for ordering in sequence
One of the advantages of using the ISO 8601ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
date format is that the lexicographical order
Lexicographical order
In mathematics, the lexicographic or lexicographical order, , is a generalization of the way the alphabetical order of words is based on the alphabetical order of letters.-Definition:Given two partially ordered sets A and B, the lexicographical order on...
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
Collation
Collation is the assembly of written information into a standard order. One common type of collation is called alphabetization, though collation is not limited to ordering letters of the alphabet...
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
Parsing
In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
Day and year only
The U.S. military sometimes uses a system, which they call "Julian date format" that indicates the year and the actual day out of the 365 days of the year (and thus a designation of the month would not be needed). For example, "11 December 1999" can be written in some contexts as "1999345" or "99345", for the 345th day of 1999. This system is most often used in US military logistics, since it makes the process of calculating estimated shipping and arrival dates easier. For example: say a tank engine takes an estimated 35 days to ship by sea from the US to Korea. If the engine is sent on 99104, it should arrive on 99139. Note that outside of the US military and some US government agencies, including the Internal Revenue ServiceInternal Revenue Service
The Internal Revenue Service is the revenue service of the United States federal government. The agency is a bureau of the Department of the Treasury, and is under the immediate direction of the Commissioner of Internal Revenue...
, this format is usually referred to as "ordinal date
Ordinal date
An ordinal date is a calendar date typically consisting of a year and a day of year ranging between 1 and 366 , though year may sometimes be omitted...
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
OS/390
OS/390 is an IBM operating system for the System/390 IBM mainframe computers.OS/390 was introduced in late 1995 in an effort, led by the late Randy Stelman, to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package...
or its successor, z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
Week number used
Companies in Europe often use year, week number and day for planning purposes.So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
ISO week date
The ISO week date system is a leap week calendar system that is part of the ISO 8601 date and time standard. The system is used in government and business for fiscal years, as well as in timekeeping....
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
Expressing dates in spoken English
In British EnglishBritish English
British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
Ordinal number (linguistics)
In linguistics, ordinal numbers are the words representing the rank of a number with respect to some order, in particular order or position . Its use may refer to size, importance, chronology, etc...
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
External links
- IETF: RFC 3339
- W3C Date and Time Formats Internet date/time format
A date in a calendar is a reference to a particular day represented within a calendar
Calendar
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
Japan Standard Time
Japan Standard Time or JST is the standard timezone of Japan, and is 9 hours ahead of UTC. For example, when it is midnight in UTC, it is 09:00 in Japan Standard Time. There is no daylight saving time, though its introduction has been debated several times. Japan Standard Time is the same as...
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...
, with era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...
referring to the particular period of time (Note the different use
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
of the terms in geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
).
The most widely used epoch is a conventional
Convention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
birthdate of Jesus (which was established by Dionysius Exiguus
Dionysius Exiguus
Dionysius Exiguus was a 6th-century monk born in Scythia Minor, modern Dobruja shared by Romania and Bulgaria. He was a member of the Scythian monks community concentrated in Tomis, the major city of Scythia Minor...
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
Date format
Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endianness
Endianness
In computing, the term endian or endianness refers to the ordering of individually addressable sub-components within the representation of a larger data item as stored in external memory . Each sub-component in the representation has a unique degree of significance, like the place value of digits...
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Little endian forms, starting with the day
This sequence is common to the vast majority of the world's countries. This date format originates from the custom of writing the date as 'the 9th day of November in the year of our Lord 2003' in western religious and legal documents, which at one time were the majority of documents created. The format has shortened over time but the order of the elements has remained constant.- "9 November 2003" or "9. November 2003" (the latter is common in German-speaking regions)
- 9/11/2003 or 9.11.2003
- 09-Nov-2003 (used in the USA)
- 9-11-2003 (used in IrelandIrelandIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and the United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and is accepted in South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
& New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
) - [The] 9th [of] November 2003 (The 'of' and 'the' may be included in speech; they are omitted in all but the most formal writing.)
- Sunday, 9 November 2003
- 9/xi/03, 9.xi.03, 9-xi.03, or 9.XI.2003 (using the Roman numeralRoman numeralsThe numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
for the month) – This is usually confined to handwriting only and is not put into any form of print. It is associated with a number of schools and universities. It has also been used by the Vatican as an alternative to using months named after Roman deities. - 9 November ADAnno Dominiand Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....
2003
Big endian forms, starting with the year
In this format the most significant data item is written before lesser data items i.e. year before month before day. It is consistent with the big endianness of the Indian decimal numbering system, which progresses from the highest to the lowest order magnitude. That is, using this format textual orderings and chronological orderings are identical. This form is standard in Asian countries, Hungary, Sweden and the US armed forces.Examples for the 9th of November 2003:
- 2003-11-09: the ISO 8601ISO 8601ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
international standardInternational standardInternational standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...
orders the components of a date like this, and additionally uses leading zeros, for example, 0813-03-01, to be easily read and sorted by computers. It is used with UTC in the Internet date/time format (see the external link below). This format is also favoured in certain AsiaAsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
n countries, mainly East Asian countries, as well as in some European countries. The big endian convention is also frequently used in CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, but all three conventions are used there. - 2003 November 9
- 2003Nov9
- 2003Nov09
- 2003-Nov-9
- 2003-Nov-09
- 2003-Nov-9, Sunday
- 2003. 9. – The official format in HungaryHungaryHungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, point after year and day, month name with small initial. Following shorter formats also can be used: 2003. . 9., 2003. 11. 9., 2003. XI. 9. - 2003.11.9 using dots and no leading zeros, common in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
Middle endian forms, starting with the month
This sequence is used primarily in the United States, partially in Canada, and a few other countries . This date format was commonly used alongside the small endian form in the United Kingdom until the early 20th Century, and can be found in both defunct and modern print media such as the London GazetteLondon Gazette
The London Gazette is one of the official journals of record of the British government, and the most important among such official journals in the United Kingdom, in which certain statutory notices are required to be published...
and The Times
The Times
The Times is a British daily national newspaper, first published in London in 1785 under the title The Daily Universal Register . The Times and its sister paper The Sunday Times are published by Times Newspapers Limited, a subsidiary since 1981 of News International...
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
- Sunday, November 9, 2003
- November 9, 2003
- Nov. 9, 2003 or 11/9/2003
- 11-9-2003, 11.9.2003, 11.09.03, or 11/09/03
Usage issues
The many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits.For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
considers its ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
s, spreadsheet
Spreadsheet
A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
Federal Information Processing Standard
A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
Year 2000 problem
The Year 2000 problem was a problem for both digital and non-digital documentation and data storage situations which resulted from the practice of abbreviating a four-digit year to two digits.In computer programs, the practice of representing the year with two...
. Some U.S. government agencies now use ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
Old Style and New Style dates
Old Style and New Style are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January even though documents written at the time use a different start of year ; or to indicate that a date conforms to the Julian...
.
World locations by date format in use
Advantages for ordering in sequence
One of the advantages of using the ISO 8601ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
date format is that the lexicographical order
Lexicographical order
In mathematics, the lexicographic or lexicographical order, , is a generalization of the way the alphabetical order of words is based on the alphabetical order of letters.-Definition:Given two partially ordered sets A and B, the lexicographical order on...
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
Collation
Collation is the assembly of written information into a standard order. One common type of collation is called alphabetization, though collation is not limited to ordering letters of the alphabet...
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
Parsing
In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
Day and year only
The U.S. military sometimes uses a system, which they call "Julian date format" that indicates the year and the actual day out of the 365 days of the year (and thus a designation of the month would not be needed). For example, "11 December 1999" can be written in some contexts as "1999345" or "99345", for the 345th day of 1999. This system is most often used in US military logistics, since it makes the process of calculating estimated shipping and arrival dates easier. For example: say a tank engine takes an estimated 35 days to ship by sea from the US to Korea. If the engine is sent on 99104, it should arrive on 99139. Note that outside of the US military and some US government agencies, including the Internal Revenue ServiceInternal Revenue Service
The Internal Revenue Service is the revenue service of the United States federal government. The agency is a bureau of the Department of the Treasury, and is under the immediate direction of the Commissioner of Internal Revenue...
, this format is usually referred to as "ordinal date
Ordinal date
An ordinal date is a calendar date typically consisting of a year and a day of year ranging between 1 and 366 , though year may sometimes be omitted...
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
OS/390
OS/390 is an IBM operating system for the System/390 IBM mainframe computers.OS/390 was introduced in late 1995 in an effort, led by the late Randy Stelman, to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package...
or its successor, z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
Week number used
Companies in Europe often use year, week number and day for planning purposes.So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
ISO week date
The ISO week date system is a leap week calendar system that is part of the ISO 8601 date and time standard. The system is used in government and business for fiscal years, as well as in timekeeping....
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
Expressing dates in spoken English
In British EnglishBritish English
British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
Ordinal number (linguistics)
In linguistics, ordinal numbers are the words representing the rank of a number with respect to some order, in particular order or position . Its use may refer to size, importance, chronology, etc...
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
External links
- IETF: RFC 3339
- W3C Date and Time Formats Internet date/time format
A date in a calendar is a reference to a particular day represented within a calendar
Calendar
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...
system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "24 " is ten days after "14 " in the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...
. The date of a particular event depends on the observed UTC offset. For example the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
that began at 1941-12-07T18:18Z took place on 7 December according to Hawaii Time (UTC-10:30), and on 8 December according to Japan Standard Time
Japan Standard Time
Japan Standard Time or JST is the standard timezone of Japan, and is 9 hours ahead of UTC. For example, when it is midnight in UTC, it is 09:00 in Japan Standard Time. There is no daylight saving time, though its introduction has been debated several times. Japan Standard Time is the same as...
(UTC+09).
A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar
Julian calendar
The Julian calendar began in 45 BC as a reform of the Roman calendar by Julius Caesar. It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year .The Julian calendar has a regular year of 365 days divided into 12 months...
, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...
, with era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...
referring to the particular period of time (Note the different use
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
of the terms in geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
).
The most widely used epoch is a conventional
Convention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
birthdate of Jesus (which was established by Dionysius Exiguus
Dionysius Exiguus
Dionysius Exiguus was a 6th-century monk born in Scythia Minor, modern Dobruja shared by Romania and Bulgaria. He was a member of the Scythian monks community concentrated in Tomis, the major city of Scythia Minor...
in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as " " rather than " "). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.
Date format
Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endianness
Endianness
In computing, the term endian or endianness refers to the ordering of individually addressable sub-components within the representation of a larger data item as stored in external memory . Each sub-component in the representation has a unique degree of significance, like the place value of digits...
. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.
Little endian forms, starting with the day
This sequence is common to the vast majority of the world's countries. This date format originates from the custom of writing the date as 'the 9th day of November in the year of our Lord 2003' in western religious and legal documents, which at one time were the majority of documents created. The format has shortened over time but the order of the elements has remained constant.- "9 November 2003" or "9. November 2003" (the latter is common in German-speaking regions)
- 9/11/2003 or 9.11.2003
- 09-Nov-2003 (used in the USA)
- 9-11-2003 (used in IrelandIrelandIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and the United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and is accepted in South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
& New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
) - [The] 9th [of] November 2003 (The 'of' and 'the' may be included in speech; they are omitted in all but the most formal writing.)
- Sunday, 9 November 2003
- 9/xi/03, 9.xi.03, 9-xi.03, or 9.XI.2003 (using the Roman numeralRoman numeralsThe numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
for the month) – This is usually confined to handwriting only and is not put into any form of print. It is associated with a number of schools and universities. It has also been used by the Vatican as an alternative to using months named after Roman deities. - 9 November ADAnno Dominiand Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....
2003
Big endian forms, starting with the year
In this format the most significant data item is written before lesser data items i.e. year before month before day. It is consistent with the big endianness of the Indian decimal numbering system, which progresses from the highest to the lowest order magnitude. That is, using this format textual orderings and chronological orderings are identical. This form is standard in Asian countries, Hungary, Sweden and the US armed forces.Examples for the 9th of November 2003:
- 2003-11-09: the ISO 8601ISO 8601ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
international standardInternational standardInternational standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...
orders the components of a date like this, and additionally uses leading zeros, for example, 0813-03-01, to be easily read and sorted by computers. It is used with UTC in the Internet date/time format (see the external link below). This format is also favoured in certain AsiaAsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
n countries, mainly East Asian countries, as well as in some European countries. The big endian convention is also frequently used in CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, but all three conventions are used there. - 2003 November 9
- 2003Nov9
- 2003Nov09
- 2003-Nov-9
- 2003-Nov-09
- 2003-Nov-9, Sunday
- 2003. 9. – The official format in HungaryHungaryHungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, point after year and day, month name with small initial. Following shorter formats also can be used: 2003. . 9., 2003. 11. 9., 2003. XI. 9. - 2003.11.9 using dots and no leading zeros, common in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
It is also extended through the universal big-endian format clock time: 9 November 2003, 18h 14m 12s, or 2003/11/9/18:14:12 or (ISO 8601) 2003-11-09T18:14:12.
Middle endian forms, starting with the month
This sequence is used primarily in the United States, partially in Canada, and a few other countries . This date format was commonly used alongside the small endian form in the United Kingdom until the early 20th Century, and can be found in both defunct and modern print media such as the London GazetteLondon Gazette
The London Gazette is one of the official journals of record of the British government, and the most important among such official journals in the United Kingdom, in which certain statutory notices are required to be published...
and The Times
The Times
The Times is a British daily national newspaper, first published in London in 1785 under the title The Daily Universal Register . The Times and its sister paper The Sunday Times are published by Times Newspapers Limited, a subsidiary since 1981 of News International...
, respectively. In the UK, it would be verbally expressed as Sunday, November the 9th, whereas in the United States, it is usually Sunday, November 9th, although usage of "the" isn't uncommon.
- Sunday, November 9, 2003
- November 9, 2003
- Nov. 9, 2003 or 11/9/2003
- 11-9-2003, 11.9.2003, 11.09.03, or 11/09/03
Usage issues
The many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits.For example, "9/11" can refer to both the Fall of the Berlin Wall on 9 November 1989 and to September 11 attacks. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, dates are rarely written in purely numerical forms in formal writing, although they are very common elsewhere; when numerical forms are used, the month appears first. In the United Kingdom, while it is regarded as acceptable to write month-name day, year, this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11 September 2001 terrorist attacks.
When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, and so on.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example).
In addition, the ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
considers its ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard to make sense from a logical perspective. Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
s, spreadsheet
Spreadsheet
A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...
s and other software tools with built-in sorting functions.
An early U.S. Federal Information Processing Standard
Federal Information Processing Standard
A Federal Information Processing Standard is a publicly announced standardization developed by the United States federal government for use in computer systems by all non-military government agencies and by government contractors, when properly invoked and tailored on a contract...
recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem
Year 2000 problem
The Year 2000 problem was a problem for both digital and non-digital documentation and data storage situations which resulted from the practice of abbreviating a four-digit year to two digits.In computer programs, the practice of representing the year with two...
. Some U.S. government agencies now use ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
with 4-digit years.
When transitioning from one date notation to another, people often write both Old Style and New Style dates
Old Style and New Style dates
Old Style and New Style are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January even though documents written at the time use a different start of year ; or to indicate that a date conforms to the Julian...
.
World locations by date format in use
Advantages for ordering in sequence
One of the advantages of using the ISO 8601ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
standard
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
date format is that the lexicographical order
Lexicographical order
In mathematics, the lexicographic or lexicographical order, , is a generalization of the way the alphabetical order of words is based on the alphabetical order of letters.-Definition:Given two partially ordered sets A and B, the lexicographical order on...
(ASCIIbetical) of the representations is equivalent to the chronological order of the dates. Thus dates can be sorted using simple string comparison algorithms, and indeed by any left to right collation
Collation
Collation is the assembly of written information into a standard order. One common type of collation is called alphabetization, though collation is not limited to ordering letters of the alphabet...
. For example:
1998-02-28 (28 February 1998) sorts before
1999-03-01 (1 March 1999) which sorts before
2000-01-30 (30 January 2000)
The YYYY MM DD layout is the only common format that can provide this. Sorting other date representations involves some parsing
Parsing
In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...
of the date strings. This also works when a time in 24-hour format is included after the date, as long as all times are understood to be in the same time zone.
ISO 8601 is used widely where concise, human readable yet easily computable and unambiguous dates are required, although many applications store dates internally as UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
and only convert to ISO 8601 for display. It is worth noting that all modern computer Operating Systems retain date information of files outside of their titles, allowing the user to choose which format they prefer and have them sorted thus, irrespective of the files' names.
Day and year only
The U.S. military sometimes uses a system, which they call "Julian date format" that indicates the year and the actual day out of the 365 days of the year (and thus a designation of the month would not be needed). For example, "11 December 1999" can be written in some contexts as "1999345" or "99345", for the 345th day of 1999. This system is most often used in US military logistics, since it makes the process of calculating estimated shipping and arrival dates easier. For example: say a tank engine takes an estimated 35 days to ship by sea from the US to Korea. If the engine is sent on 99104, it should arrive on 99139. Note that outside of the US military and some US government agencies, including the Internal Revenue ServiceInternal Revenue Service
The Internal Revenue Service is the revenue service of the United States federal government. The agency is a bureau of the Department of the Treasury, and is under the immediate direction of the Commissioner of Internal Revenue...
, this format is usually referred to as "ordinal date
Ordinal date
An ordinal date is a calendar date typically consisting of a year and a day of year ranging between 1 and 366 , though year may sometimes be omitted...
", rather than "Julian date"
Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, for example,, "January 17" is 017 in Julian versus 0117 in month-day format. OS/390
OS/390
OS/390 is an IBM operating system for the System/390 IBM mainframe computers.OS/390 was introduced in late 1995 in an effort, led by the late Randy Stelman, to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package...
or its successor, z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
, display dates in yy.ddd format for most operations. It is important to not confuse any of these formats with UNIX time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
, which stores time as a number in seconds since 1970-01-01.
Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is highly useful to both groups of specialists. The astronomers describe their system as also being a "Julian date" system. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.
Week number used
Companies in Europe often use year, week number and day for planning purposes.So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43).
The ISO does present a standard for identifying weeks
ISO week date
The ISO week date system is a leap week calendar system that is part of the ISO 8601 date and time standard. The system is used in government and business for fiscal years, as well as in timekeeping....
, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.
Expressing dates in spoken English
In British EnglishBritish English
British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...
, full dates are usually written as 7 December 1941 (or 7th December 1941) and spoken as "the seventh of December, nineteen forty-one" (exceedingly common usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, all-numeric dates are invariably ordered dd/mm/yyyy.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the usual written form is December 7, 1941, spoken as "December seventh, nineteen forty-one" or colloquially "December the seventh, nineteen forty-one". Ordinal
Ordinal number (linguistics)
In linguistics, ordinal numbers are the words representing the rank of a number with respect to some order, in particular order or position . Its use may refer to size, importance, chronology, etc...
numerals, however, are not always used when writing and pronouncing dates, and "December seven, nineteen forty-one" is also an accepted pronunciation of the date written December 7, 1941. A notable exception to this rule is the Fourth of July.
External links
- IETF: RFC 3339
- W3C Date and Time Formats Internet date/time format