Epoch (timekeeping)

Note: This article grew out of the Epoch disambiguation page.

For epoch in the sense of an extended period of geologic time, see geologic timescale.

An epoch is the moment in time at which a timekeeping system begins to be counted. For example, the epoch of the international calendar system is the year 1 AD, while the epoch of the Islamic calendar occurred in 622 AD, and is called AH 1 in Muslim cultures.

Calendar systems

• The epoch of a calendar era is the year, day, or instant from which the later (and earlier) years of a calendar are counted.

Astronomy

• In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. The current standard epoch is J2000.0.

Technology

Computing

• In computing, an epoch is a specific date and time used as the reference for all other times. The Unix epoch is an example.

Telecommunications

• In telecommunication, an epoch date is a date in history, chosen as the reference date from which time is measured.