📖Definition
Time is measured in seconds, minutes, hours, days.
When we tell the time we can do it using the 12 hour clock or the 24 hour clock.
Diagram
am goes from 12:00 midnight to 11:59 the following morning.
pm goes from 12 noon until 11:59 that night.
Calendar
Be familiar with the calendar, especially the months which are tricky as they don't all contain the same number of days.
Diagram
💡Tips/hints
If you've got to add lengths of time together, it's often easiest to convert everything into the smallest unit, do the addition and then convert back.
If you're adding a length of time to a given time of day, first add enough time to get to an 'o'clock' and then add the remainder.
For example: John started reading at 7:25pm. If he read for 1 hour 40 minutes, at what time did he finish reading?
First get to an o'clock: 7:25pm + 35 minutes = 8 o'clock (pm). So, that leaves 1 hour 5 minutes. Add that on to 8 o'clock to see that he finished at 9:05pm.
✏️Example
Mark is travelling by train from Paris to Marseille. He leaves Paris at 0657 and arrives in Lyon at 1324. The train waits there for exactly half an hour. It then departs taking 2 hours 15 minutes to get to Marseille.
How long was the trip from Paris to Marseille?
✅Solution
Start time 0657. Arrival time 1324.
0657 to 0700 is 3 minutes.
0700 to 1324 is 6 hours 24 minutes
Now the train waits for half an hour ie. 30 minutes.
Then, there's a further 2 hours 15 minutes to get to Marseille.
So, the total journey time is 3 mins + 6 hrs 24 mins + 30 mins + 2 hrs 15 mins.
Adding the hours we get 6 + 2 = 8
Adding the minutes we get 3 + 24 + 30 + 15 = 72.
72 minutes = 1 hours 12 minutes so the total journey time is 8 hours + 1 hour 12 minutes = 9 hours 12 minutes.