Reading 24-hour clock time

In this lesson, we will learn:

• 24-hour clock time is used instead of 12-hour clock time to avoid being confused about AM or PM
• There are 24 hours in a day, so instead of the hours being labelled 1-12 AM or 1-12 PM, we can label them from 1-24 instead.
• There are rules for converting between 12-hour clock time and 24-hour clock time (and vice versa)

Notes:

• Using 12-hour clock time can be confusing because you might not know if someone is telling you a time for AM or PM (ex. is it 6 o’clock in the morning or evening?)


• By using 24-hour clock time, we can avoid the confusion of not knowing AM/PM
• There are 24 hours in a day
• The previous days ends, and the new day starts at midnight (12:00 AM)
• The middle of the day is right at noon (12:00 PM)
• For 24-hour time, you say the hours directly from 00 until 24 (or back to 00)

• This table shows all the equivalent times for the 12-hour clock and 24-hour clock:

• When it goes to midnight (12AM), it becomes 24:00 which is the same as 00:00
• Do not use this table when doing the practice questions; only for checking

• To convert from AM/PM time (12-hour clock time) to 24-hour time:

$\qquad$ 1. Minutes: stay the same
$\qquad$ 2. Hours:
• if AM, keep the same (add leading 0)
• if PM add 12

$\qquad$ 3. Exceptions: 12AM = 00h, 12PM = 12h
• Ex. (8:46AM = 08:46), (5:13PM = 17:13), (12:07AM = 00:07)


• To convert from 24-hour time to AM/PM time :

$\qquad$ 4. Minutes: stay the same
$\qquad$ 5. Hours
• if < 12, keep same, remove leading 0, and write AM
• if > 12 subtract 12 and write PM

$\qquad$ 6. Exceptions: 00:00 = 12AM and 12:00 = 12PM
• Ex. (09:54 = 9:54AM), (22:38 = 10:38PM), (00:16 = 12:16AM)