From owner-freebsd-questions@FreeBSD.ORG Sun Apr 13 02:03:32 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 16E8B37B401 for ; Sun, 13 Apr 2003 02:03:32 -0700 (PDT) Received: from out003.verizon.net (out003pub.verizon.net [206.46.170.103]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2DBD343FA3 for ; Sun, 13 Apr 2003 02:03:31 -0700 (PDT) (envelope-from tuco.email@gte.net) Received: from [192.168.1.10] ([4.65.146.231]) by out003.verizon.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20030413090328.ELKD28543.out003.verizon.net@[192.168.1.10]> for ; Sun, 13 Apr 2003 04:03:28 -0500 From: tuco To: freebsd-questions@FreeBSD.ORG Date: Sun, 13 Apr 2003 02:03:27 -0700 User-Agent: KMail/1.5 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200304130203.27417.tuco.email@gte.net> X-Authentication-Info: Submitted using SMTP AUTH at out003.verizon.net from [4.65.146.231] at Sun, 13 Apr 2003 04:03:28 -0500 Subject: Use of GMT in BSD X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 13 Apr 2003 09:03:32 -0000 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 That is, Coordinated Universal Time (UTC), the basis for all civil time, superseded GMT when the world converted to an atomic time scale and is also an internationally agreed upon time scale-- even in the UK.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)