Seconds, the 24-hour clock and timetables · Usually met around P3
The 24-hour clock
a.m. stays the same. p.m.: add 12.
How to do it
Method
a.m. stays the same. p.m.: add 12
3 p.m.: 3 + 12 = 15 → 15:00
Another way
A time line
On a time line, 3 p.m. lines up with 15:00
In full
Morning times stay as they are: 9 a.m. is 9:00 (written 09:00). For afternoon times, add 12 to the hour: 3 p.m. → 3 + 12 = 15 → 15:00. To go back, take 12 away from 13:00 to 23:00 to get the p.m. hour: 18:00 → 18 − 12 = 6 → 6 p.m. You can also match up a.m., p.m. and the 24-hour clock on a time line or a 24-hour clock face.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
2 p.m. = ?:00
Show the answer and working
Answer: 2 p.m. = 14:00
2 p.m.: afternoon hours gain 12, 2 + 12 = 14 → 14:00
Example 2
8 a.m. = ?:00
Show the answer and working
Answer: 8 a.m. = 8:00
8 a.m.: morning times stay as they are, no 12 added → 8:00 (written 08:00)
Example 3
1 a.m. = ?:00
Show the answer and working
Answer: 1 a.m. = 1:00
1 a.m.: morning times stay as they are, no 12 added → 1:00 (written 01:00)
Practise it in the game →Seconds, the 24-hour clock and timetables · Free to start, unlimited questions, no download