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).

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

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

Check out our iOS app: tons of questions to help you practice for your GCSE maths. Download free on the App Store (in-app purchases required).