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Re: timestamp resolution

From: Hans Aberg
Subject: Re: timestamp resolution
Date: Wed, 9 May 2007 13:51:16 +0200

I made a post to the moderated Usenet newsgroup sci.astro.research, "Julian day numbers and leap seconds", and there are so many responses, I cannot summarize them here.

The question of finding a good time suitable for distributed computing as well as in astronomy and sciences, plus syncing it with legal time is very complicated, and probably requires a committee of scientists and experts from a number of fields.

But one suggestion might using say TAI (International Atomic Time, with letters in French grammatical order), or possibly GPS time. It might be synced with say JD counted in seconds so that the difference becomes 0 today. Then leap seconds can be then be viewed as a feature of the UTC legal time.

TAI is the mean of highly accurate Cesium atomic clocks (the SI second is defined in terms of Cesium transitions), accuracy better than 10^-7, and is broadcast, so it can be used in computers via radio-controlled clocks (which are now commonly sold). see <http:// en.wikipedia.org/wiki/International_Atomic_Time>.

As for POSIX, I know that in some quarters, for example NASA when there is a satellite launch, one is very concerned over the problem not knowing which time the computers are set to. So it might be good to fix this gap in the POSIX standard.

  Hans Aberg

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