Measurement, time & conversions · Topic 14 of 15

Military (24-Hour) Time

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Math · 24-hour time

Four digits, no AM or PM: add 12 to 1–11 PM hours, subtract 12 from 1300 and later; midnight is 0000, noon 1200.

01 · 12-hour → 24-hourPM (1–11 o'clock): add 12

02 · 24-hour → 12-hour1300 or later: subtract 12 → PM

03 · MemorizeMidnight 0000 · noon 1200

24-hour time: 4 digits, hours (00–23) then minutes, no AM/PM must know

PM hours 1–11: add 12 (3:15 PM = 1515) must know

1300–2359 → subtract 12, it's PM (1840 = 6:40 PM) must know

AM hours 1–11: same digits, leading zero (7:05 AM = 0705)

12:xx AM → 00xx (12:25 AM = 0025)

Past 2400? Subtract 24 (2000 + 6 h = 0200)

Midnight = 0000 (2400 = end of the day); noon = 1200 must know

Same day: end time − start time (hours and minutes apart)

Borrow 1 hour = 60 minutes, not 100

Across midnight: (2400 − start) + time after 0000

4:50 PM = 1650; 2215 = 10:15 PM

Worked examples

0950 → 1410 = 4 h 20 min (not 1410 − 950 = 460)

2130 → 0315 = 2 h 30 min + 3 h 15 min = 5 h 45 min

Commonly confused

12:xx PM stays 12xx — never add 12 (12:45 PM = 1245)

Always 4 digits: 9:00 AM = 0900, not 900

Show 2 more facts

24-hour time removes the 12 a.m./12 p.m. confusion

Said in hundreds: 1400 = "fourteen hundred"

Pearl

From 1 PM on, add 12; from 1300 on, take 12 away.

Practice this topic, then test the whole section.

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