Bug 30540: Unit test

Bug 30540: Unit test

This patch adds tests for checking the output_pref method against
a timezone and datetime that would cause an Invalid local time failure

To test:
1. Apply this patch
2. Run:
   $ kshell
   k$ prove t/DateUtils.t
=> FAIL: The feature is not implemented, tests fail to complete

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 052dd948af6eaaaeeb0e83a6950543b4832aeefe)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
(cherry picked from commit 3e42ca76c28e8d4a043fbf4af1e60ad14e4fae73)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>