Answer: If the time on the clock is 12 pm, then you remove the pm and it just becomes 12.
12 am becomes 00.
Below is a comparison.
12 hour time on the left and 24 hour time on the right.
12: 00 am --> 00: 00
1: 00 am --> 1: 00
2: 00 am --> 2: 00
3: 00 am --> 3: 00
4: 00 am --> 4: 00
5: 00 am --> 5: 00
6: 00 am --> 6: 00
7: 00 am --> 7: 00
8: 00 am --> 8: 00
9: 00 am --> 9: 00
10: 00 am --> 10: 00
11: 00 am --> 11: 00
12: 00 pm --> 12: 00
1: 00 pm --> 13: 00
2: 00 pm --> 14: 00
3: 00 pm --> 15: 00
4: 00 pm --> 16: 00
5: 00 pm --> 17: 00
6: 00 pm --> 18: 00
7: 00 pm --> 19: 00
8: 00 pm --> 20: 00
9: 00 pm --> 21: 00
10: 00 pm --> 22: 00
11: 00 pm --> 23: 00