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Time is divided up into units. There are:

• 60 seconds in a minute;

• 60 minutes in an hour;

• 24 hours in a day;

• 365 days in a year.

In a leap year, which takes place every 4 years, there are 366 days. The extra day in a leap year is added at the end of February (February 29th). For the rest of this century, leap years happen if the year can be divided by 4.

Months are of varying length: January (31 days); February (28 days, 29 in a leap year); March (31); April (30); May (31); June (30); July (31); August (31); September (30); October (31); November (30) and December (31).

There are 7 days in a week. For calculation purposes, there are 52 weeks in a year.

A day is divided up into AM and PM. Note that 12 noon, or midday, is actually 12pm and that midnight is 12am.

A 24-hour clock has 4 digits (add a leading 0 if necessary: 9.25am becomes 0925). If the time is in the afternoon, add 12 to the hours (3.45pm becomes 1545).

At midnight, the day starts again as 12am (or 0000, in 24-hour clock).

Example 1

A train is due to leave London Euston at 10.50am and arrive in Wigan some 3 hours 40 minutes later. What time will it arrive in Wigan? Give the time as am/pm.

10.50am plus 3 hours is 1.50pm.

Use 10 minutes of the remaining 40 minutes to make it 2.00pm.

That leaves 30 minutes, so it arrives at 2.30pm.

Answer: 2.30pm

Example 2

Jack is told that the time is five minutes to three in the afternoon. What time is this using the 24-hour clock?

Five minutes to three is 2.55pm. For the 24 hour clock, add 12 hours for 1455.

Answer: 1455

See also Speed and Rates of Pay