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>