Move this function from maintab.cpp to qthelper.cpp. Since the
functionality was used in numerous places, use the helper function
there as well. This removes a number of inconsistencies. For example,
sometime setTimeSpec(Qt::UTC) was called, even though the
QDateTime object was already created with that time spec.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
f63485b444