A free Grade 3 math worksheet on 12-hour and 24-hour time: what a.m. and p.m. mean, why the 24-hour clock counts from 00:00 at midnight to 23:59, adding or subtracting 12 to change afternoon and evening times, the special cases of noon and midnight, and reading real timetables for trains and buses. Students match, convert both ways, answer timetable questions and explain the rule. Includes a timed lesson plan, a six-activity worksheet, an editable Word version and answer key.
Students learn that the same time can be written in two ways. On a 12-hour clock, a.m. means the hours after midnight and before noon, and p.m. means the hours after noon. On a 24-hour clock, the hours keep counting after 12, so 3:00 p.m. becomes 15:00. Students practice changing times both ways, learn the tricky cases of noon (12:00) and midnight (00:00), and use the 24-hour clock to read train and bus timetables.
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Support: give students a two-row conversion strip (1 p.m. = 13:00 up to 11 p.m. = 23:00) to use. Challenge: students make their own timetable for a school day using the 24-hour clock and write five questions about it.
Activities 1 to 5 check converting and reading 24-hour times (answer key included). Activity 6 shows whether students can explain the rule and solve a timetable problem.
Students often write 12:30 a.m. as 12:30. Use the timeline to show that the first hour after midnight is 00 on the 24-hour clock. Also show that 24-hour times always have four digits, so morning times start with 0 (08:15).
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