Building number confidence: Time
5. Converting between 12-hour and 24-hour time
The first 12 hours are the same in both systems, just written differently:
8 am = 08:00
12-hour to 24-hour time
Add 12 to afternoon (pm) hours:
3 pm = 3 +12 = 15:00 hrs
24-hour to 12-hour time:
Subtract 12 from hours greater than 12.
13:00 hrs = 13 – 12 = 1 pm
Time check
Using 24-hour time, how would you write 7 minutes past 10 in the evening?
22:07 hrs (10 + 12 = 22).
How would you say 16:45 hrs, using the 12-hour clock system?
16 is greater than 12, so 16-12 = 4, so the time is 4.45 pm, or quarter to 5 in the afternoon (when the minute hand points at 9, there are 15 minutes, or quarter of an hour, until the next hour).