[ep-uh
k or, especially Brit., ee-pok] 
| 1. | a particular period of time marked by distinctive features, events, etc.: The treaty ushered in an epoch of peace and good will. |
| 2. | the beginning of a distinctive period in the history of anything: The splitting of the atom marked an epoch in scientific discovery. |
| 3. | a point of time distinguished by a particular event or state of affairs; a memorable date: His coming of age was an epoch in his life. |
| 4. | Geology. any of several divisions of a geologic period during which a geologic series is formed. Compare age (def. 12). |
| 5. | Astronomy.
|
| 6. | Physics. the displacement from zero at zero time of a body undergoing simple harmonic motion. |
| ep·och (ěp'ək, ē'pŏk') n.
[Medieval Latin epocha, measure of time, from Greek epokhē, a point in time; see segh- in Indo-European roots.] |
epoch
1.
Under most Unix versions the epoch is 1970-01-01 00:00:00 GMT; under VMS, it's 1858-11-17 00:00:00 (the base date of the US Naval Observatory's ephemerides); on a Macintosh, it's 1904-01-01 00:00:00.
System time is measured in seconds or ticks past the epoch. Weird problems may ensue when the clock wraps around (see wrap around), which is not necessarily a rare event; on systems counting 10 ticks per second, a signed 32-bit count of ticks is good only for 0.1 * 2**31-1 seconds, or 6.8 years. The one-tick-per-second clock of Unix is good only until 2038-01-18, assuming at least some software continues to consider it signed and that word lengths don't increase by then. See also wall time.
2.
[The Jargon File]
(2004-06-10)
