Answer:
AM is easy
0100 hours = 1:00 AM
0200 hours = 2:00 AM
0300 hours = 3:00 AM
and so on
but when you get to 1200 hours = 12:00 PM
then you just keep going
example:
1300 hours = 1:00 PM
1400 hours = 2:00 PM
1500 hours = 3:00 PM
here is how i do PM
just remove the :
4:00 becomes 400
then add 1200
400 + 1200 = 1600 hours