A half-birthday is a day approximately six months before or after the real anniversary of a person's birth. It is sometimes marked by people whose birthday

Birthday

A birthday is a day or anniversary where a person celebrates his or her date of birth. Birthdays are celebrated in numerous cultures, often with a gift, party or rite of passage. Although the major religions celebrate the birth of their founders , Christmas – which is celebrated widely by...

falls near public holidays whose celebration can overwhelm private anniversaries, such as Christmas. It may also be marked by students whose birthday does not occur during the school year; a half-birthday allows a celebration with friends and teachers at school.

Calculation

There are two ways to calculate half-birthdays. The easiest way is to take the number of the date of the birthday and advance the month by six, e.g. December 3 becomes June 3. However, because not all months have the same number of days, this doesn't always work – for example, six months after August 30 birthday would be February 30, which doesn't exist.

The precise method is to add half the number of days in a year to the birth date. In the case of a common year, this would be 182.5 days. In leap years, the number of days would be 183. Continuing the example in the paragraph above, this method this would lead to a March 1 or February 29 half-birthday for an August 30 birthday, depending on whether it's a leap year.