Maths · Suggested Grade 4
12-Hour and 24-Hour Time: Class 4 Examples & Practice
12:00 AM is midnight, but 12:00 PM is noon. Those two exceptions explain why simply adding 12 to every PM time gives wrong answers.
Original explanations and practice by BananaLearn · Published 31 October 2026
On a small screen, swipe across the illustration to read every label.
Two ways to name the same moment
A 12-hour clock labels the hours 1 to 12 and adds AM or PM. AM covers midnight up to before noon; PM covers noon up to before the next midnight. A 24-hour clock records hours from 00 to 23, so the day does not need AM or PM labels.
Minutes do not change when you convert. The 35 minutes in 7:35 PM remain 35 minutes in 19:35. A leading zero makes an early hour unambiguous in a timetable: 7:05 AM is written 07:05. We use 00:00 for the beginning of a day and include a date when midnight could be misunderstood.
The four conversion cases
For 1 to 11 AM, keep the hour and use two digits if needed: 8:20 AM becomes 08:20. For 12 AM, replace 12 by 00: 12:20 AM becomes 00:20. For 12 PM, keep 12: 12:20 PM becomes 12:20. For 1 to 11 PM, add 12: 8:20 PM becomes 20:20.
The important choice is which case applies. Do not write 24:20 for 12:20 PM, and do not write 00:20 for noon. Some transport systems use 24:00 for the end of a stated date; this beginner guide uses 00:00 with the following date instead, so the calendar boundary is explicit.
Worked example: convert an afternoon activity
Football starts at 4:45 PM. Because 4 is between 1 and 11 and the label is PM, add 12 to the hour: 4 + 12 = 16. The start is 16:45. The minute part stays 45; this is conversion of a time label, not addition of a duration.
To convert 16:45 back, subtract 12 from the hour because it is greater than 12. This gives 4:45 PM. Reverse-checking is useful: if your answer returns to a different AM/PM label, the original conversion needs checking. The number 16 does not mean sixteen hours have passed since the activity began.
Worked example: midnight and the date
A coach departs at 00:15 on Tuesday. This is 12:15 AM on Tuesday, shortly after Monday has ended. It is not Tuesday lunchtime. If a message only says midnight Tuesday, ask for the date and a 24-hour time rather than guessing which evening the writer means.
Draw the boundary: Monday 23:50, Tuesday 00:00, Tuesday 00:15. The first gap is 10 minutes and the second is 15 minutes. That also shows why subtracting the displayed hour numbers directly is not a sensible elapsed-time method across midnight.
Worked example: read a short timetable
A train leaves at 09:35 and arrives at 11:10. Read these as 9:35 AM and 11:10 AM. Count 25 minutes to 10:00, then 60 minutes to 11:00, then 10 minutes to 11:10: the journey lasts 95 minutes, or 1 hour 35 minutes.
A later service departs at 14:35, which is 2:35 PM. A 24-hour label makes these services easier to distinguish. Keep time conversion separate from duration: 14:35 is a moment, while 95 minutes is an amount of time. Our elapsed-time guide develops more crossing-hour problems.
Mistakes a clock drawing can reveal
If a learner changes 7:50 PM to 19:62, check whether 12 was added to minutes as well as hours. If 12:30 AM becomes 12:30 at noon, return to the day boundary. If 13:00 is called 3 PM, partition the hour into 12 + 1 rather than looking only at its last digit.
An analogue clock repeats its face twice every day. A drawing of its hands alone cannot tell you AM or PM. Supply a context, such as breakfast or an evening journey, or give the label directly. Otherwise both morning and evening answers may be reasonable.
Make a one-day schedule, then check it
Choose five familiar activities and record their times in both formats. Include one morning activity, noon, an afternoon activity, an evening activity and midnight with a date. Compare the order on a full-day number line, not just on the circular clock face.
For a quick understanding check, ask why 12:05 PM stays 12:05 but 1:05 PM becomes 13:05. A child who explains the noon boundary has a stronger method than one who remembers add 12 as a universal rule. Keep calculations short enough to explain before adding complex timetables.
Make your own daily timetable
Copy the record into a notebook or use it to organise your own answer. Blank spaces are for your work.
| Activity and date | 12-hour time | 24-hour time |
|---|---|---|
| Morning activity | ___ | ___ |
| Noon | 12:00 PM | 12:00 |
| Afternoon activity | ___ | ___ |
| Midnight at the start of the next date | 12:00 AM | 00:00 |
10 questions with explained answers
Try the questions before opening the answers. Explain the reason, then try a changed example to check your understanding.
Convert 6:25 AM.
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06:25
An AM hour from 1 to 11 stays the same.Convert 6:25 PM.
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18:25
Add 12 to 6; keep the minutes.Convert 12:40 AM.
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00:40
This is forty minutes after midnight.Convert 12:40 PM.
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12:40
Noon keeps the hour 12.Write 21:05 in 12-hour form.
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9:05 PM
21 − 12 = 9.Write 00:05 in 12-hour form.
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12:05 AM
00 labels the midnight hour.Write 11:59 in 12-hour form.
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11:59 AM
This is just before noon.What time follows Monday 23:59 by one minute?
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Tuesday 00:00
The day changes at midnight.A lesson runs from 15:20 to 16:05. How long?
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45 minutes
40 minutes to 16:00, then 5 more.Can a clock face showing 3:00 tell you AM or PM by itself?
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No
Its hands repeat their positions twice per day; context is needed.
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