Date: Sun, 13 Apr 2003 02:03:27 -0700 From: tuco <tuco.email@gte.net> To: freebsd-questions@FreeBSD.ORG Subject: Use of GMT in BSD Message-ID: <200304130203.27417.tuco.email@gte.net>
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Hi I see GMT being used in FreeBSD and wonder why an old astronomical time scale that has been obsolete for a long time now as the basis for the World's civil time is still used? That is, Coordinated Universal Time (UTC), the basis for all civil time, superseded GMT when the world converted to an atomic time scale and is also an internationally agreed upon time scale-- even in the UK. I know GMT is steeped in tradition and has meant a different time to different people in the past but it is not technically correct to say GMT because it really means UTC when you say it. No master clock measures GMT anymore because these clocks are atomic clock measuring International Atomic Time (TAI) and UTC is derived from TAI. To the resolution of a stratum 2, NTP time server you can run on FreeBSD, GMT and UTC are different times. In fract, the time your stratum 2 server gets from the stratum 1 servers is UTC. Identifying your time scale is similar to identifying your units in, say, a measurement of length. Thanx for your attention tuco Seattle, WA REFERENCES: ----------- Explanatory Supplement to the Astronomical Almanac, U.S Naval Observatory, Chapter 2 - Time. 1992. http://maia.usno.navy.mil/bulletin-a.html -- Notice the absence of GMT here http://www.physics.nist.gov/ -- One agency that maintains the time standard. Note the absence of GMT. http://tycho.usno.navy.mil/systime.html -- Definitions of the many time scales. Note the absence of GMT. NBS Frequency and Time Broadcast Services, Radio Stations WWV, WWVH, WWVB, Special Publication 236, 1972 Edition. ( yes,that long ago)
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