Early   7:00    7:01
early is earlier than late.
Late  23:56  23:57  23:58  23:59  0:00  0:01  0:02  0:03  0:04  0:05
late is earlier than early.
early and alsoearly: Equal
equal
early and late: Unequal
unequal
Now for adding (non-member function)
22:34 plus 1:15 is 23:49
Now for subtracting (member function)
22:34 minus 1:15 is 21:19
Other way around 1:15 minus 22:34 is 2:41
23:54 plus 1:15 is 1:09