Use DateTime objects uniformly, improve expires parsing

Always use DateTime objects for every date field in the database,
and translate them into the local time zone for display when
pulling them out of the database.  This should provide better
portability to different database backends.

Change the parsing of expires arguments to use Date::Parse, thus
supporting a much broader variety of possible date and time
formats and allowing easy conversion to a DateTime object.
Document the new dependency.

Change-Id: I2ee8eaa6aa6ae9925ac419e49234ec9880d4fe95
Reviewed-on: https://gerrit.stanford.edu/1555
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: Russ Allbery <rra@stanford.edu>

0 files changed, 0 insertions, 0 deletions