A new epoch...
... a friend was asking what an epoch
is.
I went hunting for the definition of an epoch
today. I know that it can be defined as a precise amount of time as well as all
it's other uses. I have found that it is a division of a geological period but
that source told me neither how long a period is or what division of it an epoch
is <sigh>.I did, however find this
which raised a smile:Epoch
n. [Unix: prob. from astronomical timekeeping]
The time and date corresponding to 0 in an operating system's clock and
timestamp values. Under most Unix versions the epoch is 00:00:00 GMT, January 1,
1970; under VMS, it's 00:00:00 of November 17, 1858 (base date of the U.S. Naval
Observatory's ephemerides); on a Macintosh, it's the midnight beginning January
1 1904. 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 6.8 years.The
1-tick-per-second clock of Unix is good only until January 18, 2038, assuming at
least some software continues to consider it signed and that word lengths don't
increase by then. See also wall time. Microsoft Windows, on the other hand,
has an epoch problem every 49.7 days - but this is seldom noticed as Windows is
almost incapable of staying up continuously for that long.
Posted: 09:54 PM
