The 12 and 24 hour clock | Year 4 Mathematics PDF Download

Analogue and Digital Clocks

• An analogue clock, with hands, displays numbers from 1 to 12, while a digital clock shows 24-hour time format.

The 12-Hour Clock

• An analog clock displays numbers 1 to 12, representing the 24-hour day divided into two halves.
• The first 12 hours, from midnight to noon, are referred to as AM (ante meridiem), while the following 12 hours, from noon back to midnight, are referred to as PM (post meridiem).
• AM indicates "before midday" and PM indicates "after midday".
• To refer to events in the morning, we use the time followed by "AM". For example, "I have breakfast at 8 o'clock AM".
  
• For events in the afternoon or evening, we use the time followed by "PM". For instance, "I go to bed at 7 o'clock PM".
  

The 24 hour clock

• We also use the 24-hour clock to tell time without using AM and PM. It always displays four digits and is commonly used on digital clocks.
• For times before 10 o'clock in the morning, a leading zero is added. The first two digits represent the hour and the last two digits represent the minutes.
• In the 24-hour clock system, all hours in a day are represented without AM or PM indicators.
• For example:
  • 06:45 means it's 45 minutes past 6 o'clock in the morning, or 6:45 AM.
  • 12:30 means it's 30 minutes past 12 o'clock noon, or 12:30 PM.
    

Changing between 12 and 24 hour clocks

• Converting from the 12-hour clock to the 24-hour clock is straightforward: simply add 12 to the hours after midday.
• For example:
  • 2 o'clock PM becomes 14:00, as 2 + 12 = 14.
  • 8 o'clock PM becomes 20:00, as 8 + 12 = 20.
• To convert from the 24-hour clock to the 12-hour clock, particularly for PM times, subtract 12 from the hours.
• For example:
  • 19:00 becomes 7 o'clock PM, as 19 - 12 = 7.