Page 122 - Viva

Conversion of 24-Hour Clock Time to 12-Hour Clock Time
• If the given time is between 0000 hours and 0059 hours, add 1200 hours and a.m.
to it.

For example, 0050 hours = 0050 hours + 1200 hours = 1250 hours = 12:50 a.m.

0030 hours = 0030 hours + 1200 hours = 1230 hours = 12:30 a.m.
• If the given time is between 0100 hours and 1159 hours, just add a.m. to it.

For example, 1040 hours = 10:40 a.m. and 1150 hours = 11:50 a.m.
• If the given time is between 1200 hours and 1259 hours, just add p.m. to it.

For example, 1220 hours = 12:20 p.m. and 1245 hours = 12:45 p.m.

• If the given time is between 1300 hours and 2359 hours, subtract 1200 hours and
add p.m. to it.
For example, 1305 hours = 1305 hours – 1200 hours = 0105 hours = 1:05 p.m.

2315 hours = 2315 hours – 1200 hours = 1115 hours = 11:15 p.m.

Example 6: Convert the given 24-hour time to 12-hour time.
(a) 0025 hours (b) 2205 hours

Solution: (a) 0025 hours + 1200 hours = 1225 hours = 12:25 a.m.

(b) 2205 hours – 1200 hours = 1005 hours = 10:05 p.m.

Conversion of 12-Hour Clock Time to 24-Hour Clock Time
• If the given time is between 12:00 midnight and 12:59 a.m., subtract 12 hours (12:00)

from it.
For example, 12:35 a.m. = 1235 hours – 1200 hours = 0035 hours or 00:35

• If the given time is between 1:00 a.m. and 12:59 p.m., write it as it is.
For example, 11:30 a.m. = 1130 hours or 11:30

• If the given time is between 1:00 p.m. and 11:59 p.m., add 12 hours (12:00) to it.

For example, 4:20 p.m. = 0420 hours + 1200 hours = 1620 hours or 16:20
Example 7: Convert the given 12-hour time to 24-hour time.

(a) 3:15 p.m. (b) 12:15 a.m.

Solution: (a) 3:15 p.m. = 0315 hours + 1200 hours = 1515 hours or 15:15
(b) 12:15 a.m. = 1215 hours – 1200 hours = 0015 hours or 00:15

Advantages of 24-Hour Clock over 12-Hour Clock
• There is less confusion between morning and evening. For example, 7 o’clock does

not clarify the time of the day whereas 1900 hours is clearly an evening time.
2400 hours is clearly midnight and 1200 hours is noon without confusion.

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