Time
Time is measured using standard units and notations. Being able to use time notation correctly and recall basic time facts is essential for solving problems involving schedules, timetables and durations.
12-Hour and 24-Hour Clock Notation
The 12-hour clock divides the day into two parts.
Times are written with:
am for times from midnight to just before midday
pm for times from midday to just before midnight
Examples include 7:30 am and 4:45 pm.
The 24-hour clock counts continuously from midnight.
Times are written using four digits and do not use am or pm.
For example:
• 7:30 am is written as 07:30
• 4:45 pm is written as 16:45
The first two digits show the hours and the last two digits show the minutes
When converting from 12-hour to 24-hour time:
• add 12 to the hour for pm times, except for 12 pm
• midnight is written as 00:00
Understanding both systems allows times to be read and written accurately.
Standard Units of Time
Time is measured using fixed units that must be remembered.
There are:
• 60 seconds in a minute
• 60 minutes in an hour
• 24 hours in a day
• 7 days in a week
• 12 months in a year
These facts are used when converting between units of time.
Using Time Units
When working with time, it is important to:
• choose the correct unit
• convert units accurately
• read clocks and timetables carefully
For example, converting hours into minutes requires multiplying by 60.
Understanding how units of time relate to each other helps solve real life problems involving duration and schedules.
Key Points to Remember
The 12-hour clock uses am and pm.
The 24-hour clock uses four digit times and no am or pm.
There are 60 seconds in a minute and 60 minutes in an hour.
There are 24 hours in a day and 7 days in a week.
There are 12 months in a year.
Being confident with time notation and basic time facts allows problems involving time to be solved accurately and efficiently.