Ticking Clocks and Turning Calendar
AM, PM and 24-hour time
Learn what AM and PM mean, and how the 24-hour clock works.
Your book, Maths Mela (Chapter 12), shows two girls eating a meal. Both clocks show 8:00, but one girl is eating breakfast in the morning and the other is eating dinner at night. To tell them apart, we add AM for times after midnight and before noon, and PM for times after noon and before midnight. So breakfast is at 8:00 AM and dinner at 8:00 PM.
Digital clocks often use a 24-hour clock, with no AM or PM. The hours count from 00 at midnight all the way up to 23. Morning times stay the same: 8:00 AM is 08:00, 9:45 AM is 9:45 hours, and 11:20 hours is 11:20 AM. Midnight, 12:00 AM, is 00:00 hours, and noon, 12:00 PM, is 12:00 hours.
For times after noon, add 12 to the hour. 1:00 PM is 1 + 12 = 13:00 hours. 3:00 PM is 15:00 hours. 5:20 PM is 17:20 hours. 8:00 PM is 20:00 hours, and 11:45 PM is 23:45 hours.
To go back from the 24-hour clock, take away 12 from any hour bigger than 12 and write PM. 20:00 hours is 20 - 12 = 8, so 8:00 PM.
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