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From: "Eric S. Raymond" <esr@thyrsus.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Jeff King <peff@peff.net>, Shawn Pearce <spearce@spearce.org>,
	Felipe Contreras <felipe.contreras@gmail.com>,
	git <git@vger.kernel.org>
Subject: Re: Millisecond precision in timestamps?
Date: Wed, 28 Nov 2012 02:58:08 -0500	[thread overview]
Message-ID: <20121128075807.GA9912@thyrsus.com> (raw)
In-Reply-To: <7v7gp6i3rx.fsf@alter.siamese.dyndns.org>

Junio C Hamano <gitster@pobox.com>:
> Roundtrip conversions may benefit from sub-second timestamps, but
> personally I think negative timestamps are more interesting and of
> practical use. 

You mean, as in times before the Unix epoch 1970-01-01T00:00:00Z?  

Interesting.  I hadn't thought of that.  I've never seen a software
project under version control with bits that old, which is significant
because I've probably done more digging into ancient software than
anybody other than a specialist historian or two.

They would have to have been restrospective dates from the get-go.
SCCS wasn't built until 1972.

> And if we were to add "committer-timestamp" and friends to support
> negative timestamps anyway (because older tools will not support
> them), supporting sub-second part might be something we want to
> think about at the same time.

That seems eminently reasonable.

> We would however need to be extra careful.  How should we express
> half-second past Tue Nov 27 23:24:16 2012 (US/Pacific)?  Would we
> spell it 1354087456.5?  1354087456.500?  Would we require decimal
> representation of floating point numbers to be normalized in some
> way (e.g. minimum number of digits without losing precision)?  The
> same timestamp needs to be expressed the same way, or we will end up
> with different commit objects, which defeats the whole purpose of
> introducing subsecond timestamps to support round-trip conversions.
> 
> If we were to use a separate "subsecond" fields, another thing we
> need to be careful about is the order of these extra fields, exactly
> for the same reason.

I think minimum number of digits without losing precision is about the
only alternative that is future-proof - I was going to suggest it for
that reason.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>

  reply	other threads:[~2012-11-28  7:58 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-27 20:48 Millisecond precision in timestamps? Eric S. Raymond
2012-11-27 21:41 ` Shawn Pearce
2012-11-27 22:06   ` Junio C Hamano
2012-11-27 23:04     ` Eric S. Raymond
2012-11-27 23:49       ` Shawn Pearce
2012-11-28  0:12         ` Eric S. Raymond
2012-11-28  0:22           ` David Lang
2012-11-28  0:26           ` Felipe Contreras
2012-11-28  1:07             ` Shawn Pearce
2012-11-28  1:17               ` Jeff King
2012-11-28  1:29                 ` Jason Pyeron
2012-11-28  1:42                 ` Felipe Contreras
2012-11-28  3:23                 ` Eric S. Raymond
2012-11-28  3:30                   ` Jeff King
2012-11-28  3:44                     ` Felipe Contreras
2012-11-28  3:47                     ` Eric S. Raymond
2012-11-28  4:07                       ` Jeff King
2012-11-28  4:25                         ` Eric S. Raymond
2012-11-28  7:29                 ` Junio C Hamano
2012-11-28  7:58                   ` Eric S. Raymond [this message]
2012-11-28  8:04                     ` David Aguilar
2012-11-28 10:14                       ` Andreas Ericsson
2012-12-05 23:37                       ` Robin Rosenberg
2012-12-10 20:56                     ` James Cloos
2012-11-28  8:19                   ` Thomas Berg
2012-11-28  8:44                     ` Felipe Contreras
2012-11-28  9:10                       ` Thomas Berg
     [not found]                         ` <E4C993F4-B7A4-4CB6-A9EA-BFE98BE3A381@gmail.com>
2012-11-29  6:16                           ` Eric S. Raymond
2012-11-29  7:11                           ` Junio C Hamano
2012-11-29  7:22                             ` Felipe Contreras
2012-11-29 10:38                               ` Eric S. Raymond
2012-11-29 16:42                                 ` Junio C Hamano
2012-11-29 19:02                                   ` Eric S. Raymond
2012-11-28 17:57                     ` Junio C Hamano
2012-11-28 10:10                   ` Andreas Ericsson
2012-11-29 19:14                   ` Phil Hord
2012-11-29 20:01                     ` Jeff King
2012-11-28  1:11             ` Eric S. Raymond
2012-11-28  1:36               ` Felipe Contreras
2012-11-28  2:01       ` Junio C Hamano
2012-11-27 21:44 ` Pyeron, Jason J CTR (US)

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