Units of Time
There are many units used to measure time, here are some to remember:
A year is made up of 12 months.
It is also made up of 365 days (366 in a leap year).
And it has 52 weeks.
A month is made up of either 30 or 31 days or in the case of February 28 days (but 29 in a leap year).
A week is made up of 7 days.
A day is made up of 24 hours.
An hour is made up of 60 minutes.
A minute is made up of 60 seconds.
To remember the number of days in each month it is worth learning this saying:
“30 days have September, April, June and November. All the rest have 31, except for February alone, which has 28 days clear, and 29 in a leap year.”
A leap year happens once every 4 years and the only thing that changes is that February has an extra day.
Telling the time
There are 2 different ways of reading and writing time, the 12 hour clock, and the 24 hour clock.
The 12 hour clock
A typical 12 hour clock shows 12 hours around it’s face, like this:
The short hand points to the hours and the long hand points to the minutes.
The clock above shows the time to be half past three. This can also be written:
When reading a 12 hour clock it is important to know that each time on the clock is shown twice every day. There are 24 hours in a day and just 12 hours on the face of the clock, so the hour hand will go all the way round the clock twice every day.
From 12 midnight to 12 noon, the morning time, we call
From 12 noon until 12 midnight, the afternoon and evening time, we call
We don’t know from looking at the picture of the clock above if it is 3:30 in the morning or 3:30 in the afternoon! But if we were told it was 3:30 pm we would know it was 3:30 in the afternoon.
The 24 hour clock
The 24 hour clock shows time like this:
The 24 hour clock does not stop at 12:00 like the 12 hour clock, it keeps going to 13:00, then 14:00 and so on all the way up to 23:59.
Then at middnight it starts all over again at 00:00.
An hour after 12 midday we go to 1:00 pm on the 12 hour clock. On the 24 hour clock this looks like this:
The next hour after 13:00 is 14:00 – this is 2 pm.
In the hours before 12:00 (midday) an extra ‘0’ is added to the 24-hour clock time at the start, so 8 am looks like this:
Here is the time 3:30 pm shown on a 24 hour clock:
The hours are on 15 and the minutes on 30. This tells us it is half past three in the afternoon.
If you get confused by the hours on a 24 hour clock you can take away 12 from the hours:
15:30 – 12 = 3:30
Don’t forget it will always be pm if you have used this method of subtracting 12.
3:30 pm on the 12 hour clock and 15:30 on the 24 hour clock are the same time.
Speed is the measure of distance over time.
Speed is often measured in miles per hour (mph). Or kilometers per hour(kph).
You can think of speed as a measure of how far you can go in an hour.
Imagine that a space ship is flying up in to space, the faster it goes, the further it will get in an hour.