Epoch

Look up epoch in Wiktionary, the free dictionary.

Etymology: from Latin epocha < Ancient Greek ἐποχή (epokhē)

In periodization the term Epoch most often means "a beginning", and epochs thus define a point or moment when what comes after has begun, though some disciplines (geology) use the term as a time division like age, period, or era, meaning a defined span of time. Depending on context, epoch can refer to:

• a defining moment in the beginning of, or characteristic of, a distinctive historical period or era.
• a criteria, a type of time division of the geologic time scale based on rock layering which is less than a era (geology), age (geology), and period (geology) while being greater than a stage. (Geology also uses other spans not found in similar language contexts)
• a phase in the development of the universe with distinctive properties during the the Big Bang.
• epoch (astronomy) - a precise moment in time for which celestial coordinates or orbital elements are specified by international agreement, usually periodically reset to centennial and half-century dates. All other orbits calculations near or after the astronomical epoch are based on the epoch date.
• Many computer operating systems maintain system time based on some starting time called the epoch. For example, Unix and POSIX systems count time as seconds since January 1, 1970. See Unix time.

Proper noun

• Epoch (magazine), the literary magazine of Cornell University.
• Ha-Tsefirah (lit. Epoch), a Hebrew language newspaper published in 1862 and 1874-1931.
• Epoch (film), a science fiction film directed by Matt Codd
• Epoch Game Pocket Computer, an early hand-held game console
• Epoch Co., the maker of the above and other computer games
• Epoch (Chrono Trigger), a flying time machine in role-playing game Chrono Trigger
• Epoch (DC Comics), a supervillain also known as the Lord of Time
• Epoch (Marvel Comics), a cosmic entity in the Marvel Comics universe.
• Epoch Hunter, a boss in World of Warcraft's Caverns of Time; Old Hillsbrad Foothills.
• The Epoch Times, a privately owned Falun Gong-linked newspaper
• Epoch Javascript Calendar is an open source, GPL calendar component for use in web pages written in JavaScript.
• Epoch operating system was a European research project in the 1990s to build an operating system based on the ChorusOS operating system kernel.

Other

• a step in the training process of an artificial neural network

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