Time and Duration: AM, PM and 24-Hour Time | Year 4
30 October 2026 · Pi Leo Academy
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“How long until we leave?” is a maths question hiding in an everyday conversation. Time can feel tricky because an hour contains 60 minutes, not 100. This companion guide gives your child a clear way to work with clock times and durations.
A time tells you when; a duration tells you how long
3:20 pm is a clock time. 45 minutes is a duration. Keeping these ideas separate helps when a question asks for a start time, a finishing time or the amount of time between them.
Useful facts are 60 seconds = 1 minute, 60 minutes = 1 hour and 24 hours = 1 day. You can write these next to your working rather than trying to remember every conversion at once.
Use easy jumps on a timeline
A swimming lesson begins at 3:35 pm and finishes at 4:20 pm. How long does it last?
- Jump from 3:35 pm to 4:00 pm: that is 25 minutes.
- Jump from 4:00 pm to 4:20 pm: that is 20 minutes.
- Add the jumps: 25 + 20 = 45 minutes.
The duration is 45 minutes. Check by adding 45 minutes to the starting time. Breaking the journey at the next whole hour makes the calculation easier to follow.
AM, PM and the 24-hour clock
AM covers the time from midnight until just before noon. PM covers noon until just before midnight. 12 am is midnight; 12 pm is noon. These two labels deserve extra attention.
On a 24-hour clock, 3:35 pm is written 15:35. For afternoon and evening times from 1 pm to 11 pm, add 12 to the hour. Keep the minutes unchanged. Noon is 12:00 and midnight at the start of a day is 00:00.
A common mix-up
One hour and 30 minutes is 90 minutes, not 130 minutes. The calculation is 60 + 30. Similarly, 1.5 hours means one and a half hours: half of 60 minutes is 30 minutes.
When a journey crosses noon or midnight, label the timeline carefully. Include the day if needed, so an evening start and a morning finish are not accidentally placed on the same day.
Try two everyday questions
- A film starts at 10:50 am and finishes at 12:10 pm. How long is it?
- What time is 6:25 pm on a 24-hour clock?
Answers: 1. 1 hour 20 minutes, or 80 minutes: ten minutes to 11, sixty to 12, then ten more. 2. 18:25.
Try the same method with your family's next bus journey or sports session. Ask your child to explain each jump before adding the total.
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