What are the 12-hour and 24-hour clock?

12 and 24 hour time
We explain how primary-school children are taught to use the 12-hour and 24-hour clock to tell the time on analogue and digital clocks, and how you can support their learning at home.

What are the 12-hour and 24-hour clock?

There are two ways of telling the time:

The 12-hour clock runs from 1am to 12 noon and then from 1pm to 12 midnight.

The 24-hour clock uses the numbers 00:00 to 23:59 (midnight is 00:00).

12-hour clock 24-hour clock
1am 01.00
2am 02.00
3am 03.00
4am 04.00
5am 05.00
6am 06.00
7am 07.00
8am 08.00
9am 09.00
10am 10.00
11am 11.00
12 noon 12.00
1pm 13.00
2pm 14.00
3pm 15.00
4pm 16.00
5pm 17.00
6pm 18.00
7pm 19.00
8pm 20.00
9pm 21.00
10pm 22.00
11pm 23.00
12 midnight 24.00

Children in Year 1 learn to tell the time on a 12-hour analogue clock which looks like this:

At this point, they learn to tell the time to the hour and half hour.

In Year 2 they learn that there are 24 hours in a day, 60 minutes in an hour, and 30 minutes in half an hour. They move onto reading the time to the quarter hour and then the nearest five minutes. They also start to learn about time intervals (working out the length of time between two times).

In Year 3, children learn children learn that there are 60 seconds in a minute. They continue to tell the time with increasing speed and accuracy. Here is an example of a time interval word problem involving the 12-hour clock that they may come across:

I put some lamb in the oven at 10.30 in the morning. I take it out at 11.20 the same morning. How long has it been in the oven?

In Year 4, children need to convert between units of time (hour and minutes). They need to read, write and convert time between analogue and digital 12-hour and 24-hour clocks.

In Years 5 and 6, children are asked to solve problems involving converting between units of time. A Year 5 or 6 child may come across a problem like the following, that requires them to work out a time interval using their knowledge of both the 12-hour and 24-hour clock:

I get the 13:46 train to Manchester, which takes exactly three hours and five minutes. How many minutes before 5pm do I arrive in Manchester?

If a child was struggling with this, they may be encouraged to draw a number line in order to count forward the 3 hours and 5 minutes:

They could then convert the 24-hour clock time to 12-hour time, which would be 4:51pm. They should then be able to work out that they would arrive in Manchester 9 minutes before 5pm.