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From: pcg@cs.aber.ac.uk (Piercarlo Grandi)
Newsgroups: comp.mail.uucp
Subject: Re: UUCP status files and wierd dates.
Message-ID: <PCG.90Nov18164530@teachk.cs.aber.ac.uk>
Date: 18 Nov 90 16:45:30 GMT
References: <736@dynasys.UUCP> <803@sci34hub.UUCP> <4412@auspex.auspex.com>
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In-reply-to: guy@auspex.auspex.com's message of 16 Nov 90 19:03:20 GMT

On 16 Nov 90 19:03:20 GMT, guy@auspex.auspex.com (Guy Harris) said:

guy> January 1, 1970, midnight *GMT* (or UTC), specifically - i.e., the
guy> correct value for the internal time on *all* UNIX machines on
guy> Planet Earth, [ ... ]

guy> One reason is that, as indicated above, internal UNIX dates don't
guy> have to worry about time zones, daylight savings time, etc.

The essential reason is that UNIX was almost immediately a networked
environment (UUCP a very early development), and the internal BTL UUCP
network was spanning several time zones; this meant that all the
machines had to use the same time base for stamping files, or all sorts
of distributed sw engineering operations, like software distribution
(uucp), or distributed makes (uux make), would not work across time
zones.

DEC with VMS made the catastrophic mistake of using local time as the
time base, and any DEC VMS site that shares files with sites in other
time zones has had big big problems.

For the same reason above, Internet and UUCP mail dates are required to
be stamped wither with the GMT time or with local time and an indication
of the time zone, so that GMT time can be deduced. Otherwise, when e.g.
sorting a mailbox by date sent, some replies from another time zone
could appear before the questions...
--
Piercarlo Grandi                   | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcsun!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk