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From:	Denis Excoffier <3 DOT 1416 AT free DOT fr>
To:	cygwin AT cygwin DOT com
Reply-To:	cygwin AT denis-excoffier DOT org
Subject:	unexpected jumps to the future in the system date
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Date:	Sun, 19 Dec 2010 22:13:53 +0100
Cc:	lasse DOT collin AT tukaani DOT org, cygwin AT denis-excoffier DOT org
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Hello,

I've experienced a curious behaviour of /usr/bin/date, more especially  
some large jumps in the future.
Since i cannot formally exclude a BLODA problem, i'm not very  
comfortable at sending this, but
see the additional remarks at the end.

Program is `mytest':
---8<---------------------
#!/bin/sh

rm -f f1 f1.xz
echo "dummy text" > f1
# next line removes f1 and creates f1.xz (for those unfamiliar with  
`xz')
/usr/bin/xz -8 f1

/usr/sbin/zdump UTC
/usr/bin/date -u
/usr/bin/xz -d < f1.xz > /dev/null
/usr/bin/date -u
/usr/sbin/zdump UTC

rm -f f1 f1.xz
---8<----------------------

Result is (lines starting by # have been added by me afterwards):
---------------------------
Script started on Fri Dec 17 17:49:56 2010
jupiter% mytest
# time given by `zdump` is always correct
UTC  Fri Dec 17 16:50:00 2010 UTC
# time given by `date` is still correct here
Fri Dec 17 16:50:00 UTC 2010
#
# for `date`, there is a jump of 4.5 days!
#
Wed Dec 22 03:17:46 UTC 2010
# time given by `zdump` is always correct
UTC  Fri Dec 17 16:50:00 2010 UTC
jupiter% mytest
#
# 5 seconds later...
UTC  Fri Dec 17 16:50:05 2010 UTC
# `date` also is 5 seconds later
Wed Dec 22 03:17:51 UTC 2010
#
# now a jump of 6 seconds!
#
Wed Dec 22 03:17:57 UTC 2010
# in fact, less than 1 second has elapsed in reality
UTC  Fri Dec 17 16:50:05 2010 UTC
jupiter% mytest
#
# again 5 seconds later
UTC  Fri Dec 17 16:50:10 2010 UTC
# `date` also is 5 seconds later
Wed Dec 22 03:18:02 UTC 2010
#
# jump of 5 seconds!
#
Wed Dec 22 03:18:07 UTC 2010
# in fact, less than 1 second has elapsed in reality
UTC  Fri Dec 17 16:50:10 2010 UTC
jupiter% exit
exit

Script done on Fri Dec 17 17:50:11 2010
---------------------------

Remarks:
- i use XP, with McAfee perhaps not completely deactivated
- all versions are the last available in the mirrors:
   /usr/bin/xz, /usr/bin/zdump, /usr/bin/date, cygwin1.dll
- /usr/sbin/zdump is simply an alternate command to print the date
   it seems to remain functioning in the storm
- the -8 is an important detail: 32Mo will be needed to
   decompress the file; a similar option (eg -7 or -9) does not produce
   any weird behaviour
- i tried to replace the `xz -d' line with
   `dd bs=33M count=1 < /dev/zero > /dev/null' or similar but nothing
   special happened; also `xz -cd f1.xz > /dev/null' does not work
- this is 100% reproducible, only the jump amounts seems erratic


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