For Jens Olsen's World Clock, which is actually an astronomical clock

Astronomical clock

An astronomical clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.-Definition:...

, see Jens Olsen's World Clock

Jens Olsen's World Clock

Jens Olsen's World Clock or Verdensur is an advanced astronomical clock which is displayed in Copenhagen City Hall.The clock was designed and calculated by Jens Olsen who was a skilled locksmith, but later learned the trade of clockmaking...

A world clock, often called a "Worldtime Clock", is a clock

Clock

A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...

 which displays the time

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 for many (or all) places around the world

World

World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

.

The display can take various forms:

• The clock face
  Clock face
  A clock face is the part of an analog clock that displays the time through the use of a fixed numbered dial or dials and moving hands. In its most basic form, recognized universally throughout the world, the dial is numbered 1–12 indicating the hours in a 12-hour cycle, and a short hour hand...
  
   can incorporate multiple round analogue clocks with moving hands or multiple digital
  Digital
  A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
  
   clocks with numeric readouts, with each clock being labelled with the name of a major city or time zone in the world.
• It could also be a picture map
  Map
  A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....
  
   of the world with embedded analog or digital time-displays.
• A moving circular map of the world, rotating inside a stationary 24 hour dial ring. Alternatively, the disc can be stationary and the ring moving.
• Light projection onto a map representing daytime, used in the Geochron
  Geochron
  Geochron, Inc. is an American company founded by James Kilburg, an inventor from Luxembourg. It is also the name of their flagship product, the Geochron Global Time Indicator...
  
  , a brand of a particular form or world clock.

There are also worldtime watch

Watch

A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...

es, both wrist watches and pocket watch

Pocket watch

A pocket watch is a watch that is made to be carried in a pocket, as opposed to a wristwatch, which is strapped to the wrist. They were the most common type of watch from their development in the 16th century until wristwatches became popular after World War I during which a transitional design,...

es. Sometime manufacturers of timekeepers erroneously apply the worldtime label to instruments that merely indicate time for two or a few time zone

Time zone

A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s, but the term should be used only for timepieces that indicate time for all major time zone

Time zone

A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...

s of the globe.

External links

• The World Clock - Time zones, current local times around the world
• World Clock - current local times (requires Javascript)
• analog Worldclocks on Flat-Screen