Date: Sat, 26 Oct 2002 13:50:05 -0700 (PDT) From: Gil Kloepfer <gil@arlut.utexas.edu> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/17623: date(1) -v doesn't handle time changes (DST) correctly Message-ID: <200210262050.g9QKo5Cn008254@freefall.freebsd.org>
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The following reply was made to PR bin/17623; it has been noted by GNATS.
From: Gil Kloepfer <gil@arlut.utexas.edu>
To: freebsd-gnats-submit@FreeBSD.org
Cc:
Subject: Re: bin/17623: date(1) -v doesn't handle time changes (DST) correctly
Date: Sat, 26 Oct 2002 15:47:47 -0500
Additional information:
The documentation for the date command is also wrong because
of this bug. It says:
When a date is adjusted to a specific value or in units greater
than hours, daylight savings time considerations are ignored.
Adjustments in units of hours or less honor daylight saving time.
So, assuming the current date is March 26, 0:30 and that the DST
adjustment means that the clock goes forward at 01:00 to 02:00,
using -v +1H will adjust the date to March 26, 2:30. Likewise,
if the date is October 29, 0:30 and the DST adjustment means that
the clock goes back at 02:00 to 01:00, using -v +3H will be nec-
essary to reach October 29, 2:30.
Looking at the code, it is obvious why the above is not the case. Hours
are modified in the tm structure from localtime, instead of using the
seconds-since-epoch and then converting it to printable time (as the
bug originator pointed out).
Another example of this bug in action:
csdlap3$ date ; date -v+16H
Sat Oct 26 15:44:58 CDT 2002
Sun Oct 27 07:44:58 CST 2002
This is also wrong (the second time should be 06:44:58 CST).
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