There are two main ways we represent time over a day. 24 hour time represents time as one block of 24 hours. 12 hour time represents a day as two blocks of 12 hours each. The hours before midday add an "am" to show it's the morning and the hours after midday add on a "pm" so we know it's the afternoon.
There is also variation in how 12 and 24 hour time is displayed. 12 hour time may use "am", "a.m.", "AM" or similar variations, while 24 hour time could represent 03:15 as 3:15 or 0315 which is more common in the military.
Below is a diagram showing the conversion between 12 and 24 time. In all cases the number of minutes will be the same.
The conversions between the different units of time are:
Time calculations are similar to our normal addition and subtraction so we can use similar strategies. However, we will also use these time unit conversions, such as 60 minutes in an hour and 24 hours in a day.
Use the clock applet to play around with adding or subtracting different amounts of time. We can also change the starting time using input box.
When adding times, if the minutes add to 60 or more increase the number of hours. The time will change between pm to am whenever the hour changes from 11 to 12.
Write 9 days to hours.
Which of the following represents 30 minutes after 11:40 pm?
Kate leaves her home at 11:15 am to visit her grandmother in a different state. She arrives at her grandmother's house at 5:15 pm. How long was Kate's trip in hours?
Conversion between 12 and 24 time:
Conversions between the different units of time: