12-hour and 24-hour clock: what children learn
In this game children match 12-hour times to the same time on a 24-hour clock, from 00:05 just after midnight to 23:50 late in the evening. Matching both ways builds the habit of adding or taking away 12 for afternoon and evening times.
Enrichment: the 24-hour clock is not part of Common Core, but it is used on timetables and devices around the world.
How to play
Pick a card on the left, then the card on the right that matches it. Each game has 6 pairs. Wrong matches are counted as mistakes, and you get three stars for a game with no mistakes.
Step by step
- a.m. or p.m.?. a.m. times are from midnight to just before noon. p.m. times are from noon to just before midnight.
- Morning times. For a.m. times from 1 a.m. to 11:59 a.m., the 24-hour time uses the same hour with 4 digits: 7:40 a.m. is 07:40.
- Afternoon and evening times. For p.m. times from 1 p.m. onwards, add 12 to the hour: 3:15 p.m. is 15:15, and 9:30 p.m. is 21:30.
- Noon and midnight. 12:30 p.m. is just after noon, so it is 12:30. 12:05 a.m. is just after midnight, so it is 00:05.
Worked examples
Example 1: What is 4:45 p.m. on a 24-hour clock?
Working: p.m., so 4 + 12 = 16.
Answer: 16:45
Example 2: What is 08:10 on a 12-hour clock?
Working: The hour is less than 12, so it is morning.
Answer: 8:10 a.m.
Example 3: What is 22:20 on a 12-hour clock?
Working: 22 − 12 = 10, and it is evening.
Answer: 10:20 p.m.
Common mistakes and how to fix them
- Writing 3:15 p.m. as 13:15. Add 12, not 10: 3 + 12 = 15.
- Writing 12:05 a.m. as 12:05. Just after midnight the 24-hour clock starts again at 00:00, so it is 00:05.
- Leaving out the leading zero, writing 7:40 for 07:40. 24-hour times always have 4 digits.
Activities to try at home
- Look at the clock on the cooker or a phone set to 24-hour time.
- Read a bus or train timetable together and say each time in a.m. or p.m.
- Ask what time a favorite TV program starts in 24-hour time.
Ideas for the classroom
- Make a class 24-hour timeline of the school day.
- Students convert times from a real timetable.
- Pair analogue clock faces with 12-hour and 24-hour digital times.
Free printable game and worksheet
The free printable starts with a game sheet, such as a color-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
How should I choose this game for my learner?
Enrichment: the 24-hour clock is not part of Common Core, but it is used on timetables and devices around the world.
Is noon 12:00 a.m. or p.m.?
Noon is usually written as 12 noon or 12:00 p.m., and is 12:00 on the 24-hour clock. Midnight is 00:00.
Can it be played with a keyboard?
Yes. Tab to a card, press Enter to pick it, then pick its partner.