Two Ways to Tell the Time

Imagine you get a text from a friend that says: 'Meet me at 7:00.' Is that 7 in the morning or 7 in the evening? You have no idea! This is a real problem with the ordinary clock. The clock face only goes up to 12, so every number appears twice a day. Today you will learn a clever way to fix that problem — the 24-hour clock, where every minute of the day has its own unique number.

The 12-hour clock splits the day into two halves of 12 hours each. The first half, from midnight to just before noon, is called am. The second half, from noon to just before midnight, is called pm. The 24-hour clock never resets. It counts straight from 0 to 23, so there is no need for am or pm. We write 24-hour times with four digits and a colon, like 14:30. The first two digits are the hours and the last two are the minutes. Here are the key rules: 1. Times from midnight to 12:59 am look almost the same in both clocks. You just make sure you have four digits. So 9:15 am becomes 09:15. 2. Noon (12:00 pm) is written as 12:00 in 24-hour time — no change. 3. For any pm time after noon, add 12 to the hour. So 3:00 pm becomes 3 + 12 = 15:00. 4. To go the other way — from 24-hour back to 12-hour — if the hour is 13 or more, subtract 12 and add pm. So 19:45 becomes 19 − 12 = 7, which is 7:45 pm.