Thanks for the replies.
Unix keeps track of time by counting the number of seconds since its
epoch (Jan 1, 1970). Does WinNT/2000 operate in the same way or does
it keep track of the number of ticks since it last booted?
"David L. Mills" <email@example.com> wrote in message news:<firstname.lastname@example.org>...
> From das Buch, Chapter 13:
> "Of the three heavenly oscillators readily apparent to ancient mariners
> and astronomers - the Earth rotation about its axis, the Earth
> revolution around the Sun and the Moon revolution around the Earth -
> none of the three have the intrinsic stability, relative to modern
> technology, to serve as a standard reference oscillator. In 1967 the
> standard second was redefined as �9,192,631,770 periods of the radiation
> corresponding to the transition between the two hyperfine levels of the
> ground state of the cesium-133 atom.� Since 1972 the time and frequency
> standards of the world have been based on International Atomic Time
> (TAI), which is defined and maintained using multiple cesium-beam
> oscillators to an accuracy of a few parts in 10^15 per day, or better
> than 100 ns per year. Since modern astronomy and space science needs a
> better interpolation means than Earth angular velocity, in 1984 ET was
> redefined as TAI + 32.184 s. As will be seen later, this requires some
> means to rationalize ET and actual mean solar time."
> "The UTC timescale thus ticks in standard TAI seconds and was set TAI -
> 10 s at 0h MJD 41,318.0 according to the Julian calendar or 0h 1 January
> 1972 according to the Gregorian calendar. This established the first
> tick of the UTC era and its reckoning with these calendars.
> Subsequently, the UTC timescale has marched backward relative to the TAI
> timescale exactly one second on scheduled occasions recorded in the
> institutional memory of our civilization. Note in passing that
> leapsecond adjustments affect the number of seconds per day and thus the
> number of seconds per year. Apparently, should we choose to worry about
> it, the UTC clock, Gregorian calendar and various cosmic oscillators
> will inexorably drift apart with time until rationalized at some atomic
> epoch by some future papal bull."
> Harza wrote:
> > I read from different sources two seperate epochs for UTC. Which is
> > correct? Are the other epoch I mention here correct?
> > UTC epoch... 1 January 1601 or 1 January 1972?
> > NTP epoch... 1 January 1900
> > UNIX epoch... 1 January 1972
> > Microsoft epoch...1 January 1980 (but uses UTC internally? )