Time

Part ofMathsMeasurement

Key points

An image of a digital and analogue clock. Both clocks show the same time. The digital clock read twenty two, ten. The analogue clock reads ten minutes past ten. The analogue clock also has marking inside the dial for hours thirteen to twenty four. These hours are coloured orange.
  • Time has various units of , eg seconds, minutes, hours or days.
  • Knowing how to measure time is useful as it helps you to work out when your favourite TV show is on, how long to bake something in the oven for, or how to read a timetable to see which bus or train is the fastest to travel between two places.
  • Clocks or stopwatches can be used to measure the amount of time something lasts, for example how long it takes an athlete to complete a race in an event or training.
  • Time is measured using either the 12-hour clock or the 24-hour clock.
    • The first 12 hours of the day, from midnight to midday are called .
    • The next 12 hours, from midday back to midnight, are called .
  • A 24-hour clock doesn’t require am or pm and instead every hour is unique from 00:00 (midnight) through to 23:59
  • Each time in am or pm will have a 24-hour clock equivalent, for example 11:59 pm is the same as 23:59 on a 24-hour clock.
An image of a digital and analogue clock. Both clocks show the same time. The digital clock read twenty two, ten. The analogue clock reads ten minutes past ten. The analogue clock also has marking inside the dial for hours thirteen to twenty four. These hours are coloured orange.
Back to top

How to measure in different units of time

Time can be measured using different units:

  • seconds
  • minutes
  • hours
  • days
  • weeks
  • years

Examples

Skip image gallery
  1. Sixty seconds equals one minute. Sixty minutes equals one hour. Twenty four hours equals one day. Seven days equals one week. Three hundred and sixty five days equals one year, asterisk. Footnote: asterisk, there are three hundred and sixty six days in a leap year.

    Time is commonly measured in different units. Different conversions between one unit and another are also used. The choice of units used will depend on the timeframe being measured and what feels logical. For example, the record at a running club to run a 5 km course could be 16 minutes. If this time was written as 960 seconds instead, it would be more difficult to grasp quickly what that timeframe means.

Question

A film lasts for 2.5 hours.

How long is this in minutes?

An image of a bar model. The bar model comprises one rectangle. Written inside the rectangle: film lasts two point five hours. A brace has been placed above the rectangle and is the same length as the rectangle. Written above the brace: How many minutes, question mark. The rectangle is coloured orange.

Back to top

How to use 12-hour and 24-hour clock notation

Time is measured using either the 12-hour clock or the 24-hour clock.The 12-hour clock notation uses and to indicate morning and afternoon.

  • am is the time from 12 midnight and before 12 noon (12.00 pm is midday/noon).
  • pm is the time from 12 midday and before 12 midnight (12.00 am is midnight).

The 24-hour clock notation is the time shown as how many hours and minutes since midnight, eg 04:30 is 4 hours and 30 minutes past midnight (or 4.30 am).

  • The 24-hour clock does not require the use of am or pm and it helps to avoid confusion (ie 07.00 is different to 19.00).
  • There are a number of acceptable ways of recording times using 24-hour clock notation:
    • 6.27 am could be written just using digits 0627
    • Alternatively a separator can be used between the hours and minutes, such as 06:27 (with a colon) or 06.27 (with a full stop).
  • Afternoon is indicated by a number bigger than 12
  • Public transport times often show 24-hour clock notation.

Examples

Skip image gallery
  1. An image of an analogue clock. The minute hand is pointing to the two, for ten minutes. The hour hand is pointing to the ten. The time shows ten minutes past ten.

    Most clock faces show the digits from 1 to 12 around the perimeter . This clock reads as ‘ten past ten’.

Question

What is the time using 12-hour clock notation?

An image of a digital clock. The digital clock shows the time, twenty one, fifteen.

Back to top

How to read timetables

Public transport timetables indicate the frequency and duration of a specific journey. Bus, train, tram and underground transport systems use timetables like these to help customers choose the correct service.

  • Timetables are usually written using 24-hour clock notation.
  • The times are often recorded using four numbers without the : or . separator between the hours and minutes.
  • A – symbol is used to indicate when the service does not stop at that particular location.

Examples

Skip image gallery
  1. Example one. The image shows a timetable of departure and arrival times. The initial column has the name of a location. These are: London Euston, Watford Junction, Milton Keynes Central, Northampton, Rugby, Coventry, Birmingham International Airport, Birmingham New Street, Sandwell and Dudley, Wolverhampton. The next six columns have the times. The first column reads: zero seven ten, dash, dash, dash, dash, zero eight zero four, zero eight fifteen, zero eight twenty six, zero eight fifty two and zero nine zero seven. The second column reads: zero seven sixteen, zero seven thirty one, zero seven fifty two, dash, zero eight fifteen, zero eight twenty five, zero eight thirty six, zero eight forty eight, zero nine fifteen and zero nine twenty nine. The third column reads: zero eight ten, dash, dash, dash, dash, zero nine zero four, zero nine fifteen, zero nine twenty seven, zero nine fifty two and the final cell is blank. The fourth column reads: zero eight sixteen, zero eight thirty one, zero eight fifty two, dash, zero nine fifteen, zero nine twenty five, zero nine thirty six, zero nine forty eight, the next cell is blank, and ten seventeen. The fifth column reads: zero eight forty, dash, dash, dash, dash, zero nine thirty four, zero nine forty five, zero nine fifty six, ten fifteen and ten twenty nine. The sixth column reads: zero nine ten, dash, dash, dash, dash, ten zero four, ten fifteen, ten twenty seven, ten fifty two and eleven zero seven. Written above the six columns: departure times. The initial column, with locations, and the label departure times are coloured purple. The first, third, fourth and sixth columns are highlighted grey. The second and fifth columns are highlighted pink.

    The timetable shows the times of a train from London to Wolverhampton. How many stations does the 08:10 train stop at before reaching Birmingham New Street?

Question

A customer arrives at Randalstown at 1 pm and takes the first available service to Ballycastle.

What time are they due to arrive in Ballycastle?

The image shows a timetable of departure times. The initial column has the name of a location. These are: Antrim, Randalstown, Ballymena and Ballycastle. The next four columns have the times. The first column reads: twelve thirty, twelve forty five, thirteen zero one, and thirteen thirty nine. The second column reads: thirteen hundred hours, thirteen fifteen, thirteen thirty one and fourteen zero nine. The third column reads: fourteen hundred hours, fourteen fifteen, fourteen thirty one and fifteen zero nine. The fourth column reads: sixteen hundred hours, sixteen fifteen, sixteen thirty one and seventeen zero nine. The initial column, with locations, and the label departure times are coloured purple. The columns for the times are highlighted grey.

Back to top

Practise time measurements and reading time

Practise using time measurements and reading and understanding time with this quiz. You may need a pen and paper to help you with your answers.

Quiz

Back to top

Play Sudoku with BBC Bitesize!

Every weekday we release brand new easy, medium and hard Sudoku puzzles. Perfect for testing your skill with numbers and logic.

Play Sudoku with BBC Bitesize!
Back to top

More on Measurement

Find out more by working through a topic