12-hour and 24-hour clock

Time is measured using either the 12-hour clock or the 24-hour clock.

12-hour clock

The 12-hour clock notation uses am and pm to indicate morning and afternoon.

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

For example

  • 6.23am
  • 7.45pm

24-hour clock

The 24-hour clock does not require the use of am or pm. Afternoon is indicated by a number bigger than 12.

curriculum-key-fact
When converting from the 12-hour clock to the 24-hour clock remember: for any time after 12.59pm, add 12 to the hours.

For example

  • 6.23pm becomes (6.23 + 12) = \text{18:23}
  • 7.45pm becomes (7.45 + 12) = \text{19:45}

The 24-hour clock always uses 4 digits, so for any time before \text{10:00} a zero is placed at the beginning.

For example

  • \text{01:00} means 1.00am
  • \text{13:00} means 1.00pm
  • \text{04:00} means 4.00am
  • \text{16:00} means 4.00pm
Question

Copy and complete the following table, then check your answers.

Table to convert times in the 12-hour clock and 24-hour clock format
Completed table showing times in the 12-hour clock and 24-hour clock format