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Converting the 12-hour Clock Time to 24-hour Clock Time

Rule 1: For the time from 1:00 a.m.
to 12:59 p.m., do not change Knowledge Desk
the number. Write the time Leap Seconds
without a colon (:) and write A day isn’t exactly 24 hours long. The Earth’s
hours instead of a.m. or p.m. rotation is gradually slowing down. To keep our
For example: clocks in sync with the Earth, scientists sometimes
add a “leap second” to the clock at the end of a day.
( a) 2:00 a.m. = 0200 hours
(b) 11:38 a.m. = 1138 hours
( c) 12 noon = 1200 hours (d) 12:58 p.m. = 1258 hours

Rule 2: For the time from 1:00 p.m. to 11:59 p.m., add 1200 (12:00) hours and write hours
instead of p.m.
For example:

( a) 4:30 p.m. = 1630 hours ( 1200 hours + 0430 hours = 1630 hours)
( b) 9:00 p.m. = 2100 hours ( 1200 hours + 0900 hours = 2100 hours)
Rule 3: For the time from 12 midnight to 12:59 a.m., subtract 1200 (12:00) hours and
write the time with hours instead of a.m.

For example:
( a) 12:30 a.m. = 0030 hours ( 1230 hours – 1200 hours = 0030 hours)
( b) 12:59 a.m. = 0059 hours ( 1259 hours – 1200 hours = 0059 hours)

Example 1: Convert the following 24-hour clock time into 12-hour clock time.
( a) 0025 hours (b) 0604 hours (c) 1328 hours

Solution:
(a) 0025 hours
Here, 0025 hours lies between 0000 hours and 0059 hours.

Therefore, 0025 hours + 1200 hours = 12:25 a.m.
( b) 0604 hours
Be Aware
Here, 0604 hours < 1200 hours. For times from 0000 (or 2400) hours
Therefore, 0604 hours = 6:04 a.m. to 0059 hours, add 1200, separate

( c) 1328 hours the hours and minutes with a colon and
Here, 1328 hours > 1200 hours. write ‘a.m.’ next to it.
Therefore, 1328 hours = 1328 hours – 1200 hours = 1:28 p.m.

Example 2: Convert the following 12-hour clock time into 24-hour clock time.
( a) 3:30 p.m. (b) 4:25 a.m. (c) 12:31 a.m.
Solution:

( a) 3:30 p.m. = 1530 hours ( 1200 hours + 0330 hours = 1530 hours)
( b) 4:25 a.m. = 0425 hours
( c) 12:31 a.m. = 0031 hours ( 1231 hours – 1200 hours = 0031 hours)

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