A comparison function for #GDateTimes that is suitable as a #GCompareFunc. Both #GDateTimes must be non-null.
second #GDateTime to compare
-1, 0 or 1 if dt1 is less than, equal to or greater than dt2.
A comparison function for #GDateTimes that is suitable as a #GCompareFunc. Both #GDateTimes must be non-null.