What Is The 12-Hour And 24-Hour Clock? Explained For Teachers, Parents And Kids

This article summarizes what elementary school students will be taught about the 12-hour clock and 24-hour clock and provides some “telling the time” questions for children to practice telling digital and analog time on digital and analog clocks. 

This blog is part of our series of blogs designed for teachers, schools and parents supporting home learning.

What is the 12-hour clock?

The 12-hour clock is most commonly represented on an analog clock with the numbers 1-12; when shown on a digital clock, it is usually accompanied by a.m. (‘ante meridiem’ – Latin for ‘before midday’) or p.m. (‘post meridiem’ – Latin for ‘after midday’).

What is the 24-hour clock?

The 24-hour clock is more often shown on digital clocks and is written in a 4-digit form, with the first two digits representing the hour and the last two representing the minutes.

There is no need for a.m. or p.m. as each time represents each hour in a 24-hour day. For example, 03:00 = 3rd hour of the day, or 3 am; 14:00 = 14th hour of the day or 2pm; 18:30 = 30 minutes past the 18th hour of the day, or 6:30pm.

How to convert from a 12-hour clock to a 24-hour clock?

To convert from a 12-hour clock to a 24-hour clock, children may be taught to add 12 to the hours after midday, e.g. 3pm becomes 15:00 because 3 + 12 = 15.

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
12pm	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
12am	00:00

When do children learn about the 12-hour and 24-hour clock in elementary school?

12-hour and 24-hour clock in 1st – 4th grades.

1st grade students will learn to tell the time to the hour and half past the hour using analog and digital clocks. 

Children’s learning of time is continued into second grade, where they will tell and write the time from analog and digital clocks, to the nearest 5 minutes, using a.m. and p.m.

By the time your child is in 3rd grade, they are expected to tell and write time to the nearest minute and measure time intervals in minutes. They will learn to represent intervals of time by using number lines. This continues into 4th grade.

There are no specific objectives about time in past 4th grade.

How do the 12- and 24-hour clocks relate to other areas of math?

Children are sometimes required to read and interpret timetables (such as timings of a school day, or a bus timetable) which will often use timings either written in the 12- or 24-hour clock.

12-hour clock & 24-hour clock worksheet questions

1. What time does this clock show?

(Answer: 8:30)

2. Lily says: ‘On my clock face, the big hand is on the 4 and the little hand is between the 8 and the 9’. What is the time on Lily’s clock face?

(Answer: 20 past 8)

3. Toby went to study at 7pm. He finished one hour later. What time did he finish? Give your answer using digital 24-hour clock time.

(Answer: 20:00h)

4. These are all times on the same morning.

A: 7:56 am

B: quarter to eight

C: six minutes to eight

D: half past seven

Write the letters for the times in order, starting with the earliest.

(Answer: D, B, C, A)

5. A clock shows this time twice a day.

Tick the two digital clocks that show this time:

A: 03:45

B: 02:45

C: 09:45

D: 21:45

E: 14:45

(Answer: B and E)

If a child is struggling then this article on telling the time breaks down step by step a method for teaching time at the lower elementary grades.

Please note, this blog focuses on Edexcel maths past papers, not the AQA or OCR exam boards, nor IGCSE maths. What’s more, the focus is on GCSE maths, not A Level maths or the maths Edexcel A Level.

The content in this article was originally written by primary school teacher Sophie Barlett and has since been revised and adapted for US schools by elementary math teacher Christi Kulesza