Bug 9031: (QA follow-up) Pass the same timezone in Calendar.t

Bug 9031: (QA follow-up) Pass the same timezone in Calendar.t

We do not need to change $ENV{TZ} or call tzset.
Pass $tz too for the second date.
Replace checking the datetime hash by delta calls.
Replacing the number of minutes.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
We will still crash with:
Invalid local time for date in time zone: America/New_York
But the changes in Calendar.pm will now resolve that.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>