Old hands may recall a bug I found in gnu date a few years ago,
regarding its reporting of past dates with the -d specifier, in or
around the time of changing to summer time (see http://mail.linux.ie/
pipermail/ilug/2002-April/044341.html). Well, it appears I've found
another one, in a very similar vein.
I have a log rotation script which runs at 0:00 every day, and which
gets yesterday's date like this in a shell script:
YESTERDAY=$(/bin/date -d yesterday "+%Y/%m%d")
and it did not behave as expected when it ran at 0:00 on the Monday
after summer time came into effect (expected 2007/0325 - got 2007/0324)
To cut a long story short, date -d yesterday returns the date and
time as it was 24 hours previously and not, as I'd expect, the date
and time at the same time on the previous day. A similar logic
applies to requests such as date -d "2 days ago".
Now, I grant you, this could be regarded as a feature rather than a
bug. However, if you do
date -d "yesterday 08:00" you should get a date string returned which
represents yesterday at 08:00 and you normally do - but if you run
date between 0:00 and 0:59 and the date you're querying is on the
earlier side of the summer time transition, the day you get will be
one day earlier than expected, and I believe that with that wording
of the arguments, I can only mean "the date as it was at 08:00 on the
day before today".
Any views, before I report this to the Gnu date maintainer?
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