Revert "lib/, src/: Use local time for human-readable dates"

Revert "lib/, src/: Use local time for human-readable dates"

This reverts commit 3f5b4b56268269fefed55aa106f382037297d663.

The dates are stored as UTC, and are stored as a number of days since
Epoch.  We don't have enough precision to translate it into local time.
Using local time has caused endless issues in users.

This patch is not enough for fixing this issue completely, since
printing a date without time-zone information means that the date is a
local date, but what we're printing is a UTC date.  A future patch
should add time-zone information to the date.

For now, let's revert this change that has caused so many issues.

Fixes: 3f5b4b562682 (2024-08-01; "lib/, src/: Use local time for human-readable dates")
Link: <https://github.com/ansible/ansible/blob/devel/test/integration/targets/user/tasks/test_expires.yml#L2-L20>
Link: <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1095430>
Link: <https://lists.iana.org/hyperkitty/list/tz@iana.org/message/ENE5IFV3GAH6WK22UJ6YU57D6TQINSP5/>
Link: <https://github.com/shadow-maint/shadow/issues/1202>
Link: <https://github.com/shadow-maint/shadow/issues/1057>
Link: <https://github.com/shadow-maint/shadow/issues/939>
Link: <https://github.com/shadow-maint/shadow/pull/1058>
Link: <https://github.com/shadow-maint/shadow/pull/1059#issuecomment-2309888519>
Link: <https://github.com/shadow-maint/shadow/pull/952>
Link: <https://github.com/shadow-maint/shadow/pull/942>
Reported-by: Chris Hofstaedtler <zeha@debian.org>
Reported-by: Gus Kenion <https://github.com/kenion>
Reported-by: Alejandro Colomar <alx@kernel.org>
Reported-by: Michael Vetter <jubalh@iodoru.org>
Reported-by: Lee Garrett <lgarrett@rocketjump.eu>
Cc: Paul Eggert <eggert@cs.ucla.edu>
Cc: Tim Parenti <tim@timtimeonline.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Brian Inglis <Brian.Inglis@SystematicSW.ab.ca>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>