The 24hour clock system can be used to tell us if times are in the morning or afternoon.
Alternatively, times can be given as a.m. (morning) or p.m. (afternoon).
Think about the time at half past three in the afternoon.
In the 24hour clock system we give the number of hours since the beginning of the day for the first two digits,
and the number of minutes since the beginning of the hour for the last two digits.
In this example, you have 12 hours in the morning + 3 hours in the afternoon which makes 15 since the
start of the day.
There are 30 minutes since the beginning of the hour so the 24hour clock time is 1530.
We can also specify the part of the day by writing the time in the normal way using digits and adding
on a.m. or p.m..
If the time is in the morning we add a.m. and if the time is in the afternoon we add p.m..
In this example, the time is in the afternoon, so it would be written 3:30 p.m..
The time "half past three in the afternoon" can be written as 1530 or 3:30 p.m.
NOTE: The 24hour clock time will always contain exactly 4 digits.
Example 2
Write these times using digits and a.m. or p.m.:
(a) 1428
This is 14 hours from the beginning of the day, which means it must be in the afternoon.
Taking off the 12 hours in the morning gives 2 hours since midday, so the time is 2:28 p.m.
(b) 0742
This is 7 hours from the beginning of the day, which means it must be in the morning, so the time is 7:42 a.m.
Practice Questions
Work out the answer to each of these questions then click on the button marked
to see whether you are correct.
(a) Write the 24hour clock time 1731 using a.m. or p.m.
(b) Write 9:26 a.m. using 24hour clock time.
