GNU bug report logs - #50115
date command arithmetic involving the epoch produces "invalid date"

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#50115: closed (date command arithmetic involving the epoch
 produces "invalid date")
Date: Sat, 05 Feb 2022 21:56:01 +0000

[Message part 1 (text/plain, inline)]

Your message dated Sat, 5 Feb 2022 13:55:26 -0800
with message-id <c31c92f0-7ea6-15fa-8751-815d08ebcbfe <at> cs.ucla.edu>
and subject line Re: bug#50115: date command arithmetic involving the epoch produces "invalid date"
has caused the debbugs.gnu.org bug report #50115,
regarding date command arithmetic involving the epoch produces "invalid date"
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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50115: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=50115
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From: Jeremy Cantrell <jmcantrell <at> gmail.com>
To: bug-coreutils <at> gnu.org
Subject: date command arithmetic involving the epoch produces "invalid date"
Date: Wed, 18 Aug 2021 20:43:01 -0500

Using `date --utc --date="..."` with a date specification that
decrements by years that should result in epoch=0
(1969-12-31T23:59:59+00:00) produces an "invalid date" error message.

The following commands should illustrate the problem:

Notice that the only difference between the starting dates is 1 second.
```sh
$ date -u -d "1970-12-31T23:59:59+00:00 - 1 year"
date: invalid date ‘1970-12-31T23:59:59+00:00 - 1 year’
$ date -u -d "1970-12-31T23:59:58+00:00 - 1 year"
Wed Dec 31 11:59:58 PM UTC 1969
```

The dates are only considered invalid if they fall on epoch=0:
```sh
$ date -u -d "1971-12-31T23:59:59+00:00 - 2 year"
date: invalid date ‘1971-12-31T23:59:59+00:00 - 2 year’
$ date -u -d "1972-12-31T23:59:59+00:00 - 3 year"
date: invalid date ‘1972-12-31T23:59:59+00:00 - 3 year’
```

Going the other direction seems to work:
```sh
$ date -u -d "1969-01-01T00:00:00+00:00 + 1 year"
Thu Jan  1 12:00:00 AM UTC 1970
```

It only seems to error when decrementing by years:
```sh
 date -u -d "1970-01-01T00:00:01+00:00 - 1 second"
Thu Jan  1 12:00:00 AM UTC 1970
```

It only seems to error when using --utc, because the following works
(my time zone is America/Chicago):
```sh
$ date -d "Wed Dec 31 06:00:00 PM CST 1970 - 1 year" +%s
0
```

[Message part 3 (message/rfc822, inline)]

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jeremy Cantrell <jmcantrell <at> gmail.com>
Cc: Gnulib bugs <bug-gnulib <at> gnu.org>, 50115-done <at> debbugs.gnu.org
Subject: Re: bug#50115: date command arithmetic involving the epoch produces
 "invalid date"
Date: Sat, 5 Feb 2022 13:55:26 -0800

[Message part 4 (text/plain, inline)]

Thanks for the bug report. I installed the attached patches to Gnulib 
and to Coreutils, and the fix should be in the next Coreutils release.

[0001-parse-datetime-allow-calculations-to-yield-1.patch (text/x-patch, attachment)]

[0001-build-update-gnulib-submodule-to-latest.patch (text/x-patch, attachment)]

[0002-date-test-against-bug-50115.patch (text/x-patch, attachment)]

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