We use clocks to tell the time and calendars to track days, months, and years.
Reading a Clock
- A clock has 12 hours. The hour hand is short; the minute hand is long.
- The minute hand takes 60 minutes to go around once = 1 hour.
- 1 hour = 60 minutes; 1 minute = 60 seconds
- 12:00 noon = midday; 12:00 midnight = start of a new day.
12-Hour and 24-Hour Time
Key formulas
Duration of Time
Duration = Ending time - Starting time.
If borrowing is needed, remember 1 hour = 60 minutes.
The Calendar
- A year has 12 months and 365 days (or 366 in a leap year).
- A leap year has 366 days; February has 29 days in a leap year and 28 in others.
- The rhyme: "30 days has September, April, June, and November. All the rest have 31, except February alone."
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What time is shown when the hour hand is on 8 and the minute hand is on 6?
Minute hand on 6 = 30 minutes. Time = 8:30
A movie starts at 4:15 p.m. and ends at 6:45 p.m. How long is the movie?
Duration = 6:45 - 4:15 = 2 hours 30 minutes
How many days are in March?
March has 31 days.
Convert 3 hours 20 minutes to minutes.
(3 x 60) + 20 = 180 + 20 = 200 minutes
School starts at 8:00 a.m. and ends at 2:30 p.m. How long is the school day?
From 8:00 a.m. to 2:30 p.m. = 6 hours 30 minutes
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Common mistakes
- Mixing up a.m. and p.m. — remember, noon is 12:00 p.m. and midnight is 12:00 a.m.
- Subtracting time without borrowing (e.g., 3:10 - 1:45 should borrow: 2:70 - 1:45 = 1:25).
Summary
1 hour = 60 minutes; 1 minute = 60 seconds. A year = 12 months = 365 days. Leap years have 366 days with February having 29 days.