Time and Calendar Problems

Time is all around us

Every day you use time. You wake up at a certain time, go to school, eat lunch, and go to bed. To plan your day, you need to read clocks and work out how long things take. This lesson shows you how to solve time and calendar problems step by step.

If you would like to practise reading a clock first, take a look at Telling the Time. Then come back here to solve problems with that time.

How time fits together

Time is built from units that fit inside each other. Here are the ones you use most:

Unit	How many
1 minute	60 seconds
1 hour	60 minutes
1 day	24 hours
1 week	7 days
1 year	12 months

Notice the special number 60. There are 60 seconds in a minute and 60 minutes in an hour. That is different from counting in tens, so it takes a little practice.

Working out how long something takes

When you want to know how long something lasts, you find the time from the start to the end. The best trick is to count on.

Worked example 1. A cartoon starts at 3:00 and ends at 4:30. How long is it?

• From 3:00 to 4:00 is 1 hour.
• From 4:00 to 4:30 is 30 minutes more.
• Add them: 1 hour and 30 minutes.

So the cartoon is 1 hour 30 minutes long.

Worked example 2. A swimming lesson starts at 10:15 and ends at 11:00. How long is it?

• From 10:15 to 11:00, count the minutes: 15 + 15 + 15 = 45 minutes.

You can draw this on a number line to see the jumps:

10:15 ──+15──> 10:30 ──+15──> 10:45 ──+15──> 11:00

Three jumps of 15 minutes make 45 minutes.

a.m. and p.m.

The day is split into two halves:

• a.m. is the morning — from midnight until 12 noon.
• p.m. is the afternoon and evening — from 12 noon until midnight.

So 7 a.m. is breakfast time, and 7 p.m. is dinner time. They are both "7 o'clock," but the letters tell you which part of the day you mean.

Calendar problems

A calendar helps you count days, weeks, and months. The days of the week always go in the same order:

Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday.

Worked example 3. Today is Monday. What day will it be in 3 days?

Count on three days:

• Monday + 1 = Tuesday
• Tuesday + 1 = Wednesday
• Wednesday + 1 = Thursday

So in 3 days it will be Thursday.

Worked example 4. A holiday lasts 2 weeks. How many days is that?

One week is 7 days, so two weeks is 7 + 7 = 14 days.

Months and the year

A year has 12 months. Most months have 30 or 31 days, but February has only 28 days (and 29 in a special "leap year" every four years). Here is a quick way to remember the order:

January, February, March, April, May, June, July, August, September, October, November, December.

If your birthday is in March and a friend's is in June, how many months apart are they? Count on: March → April (1) → May (2) → June (3). They are 3 months apart.

Practice activity

Try these on paper. Draw a number line if it helps!

1. How many minutes are there in 2 hours?
2. A game starts at 2:00 and ends at 3:15. How long is it?
3. Today is Wednesday. What day will it be in 4 days?
4. How many days are there in 3 weeks?
5. How many months are between May and September?

Answers: 1) 120 minutes (60 + 60) 2) 1 hour 15 minutes 3) Sunday 4) 21 days (7 + 7 + 7) 5) 4 months (June, July, August, September).

Why this matters

Telling the time and using a calendar help you all day, every day. You use them to catch a bus, to know when your favourite show starts, to count down to your birthday, and to be on time for school. When you can count on from a start time and read a calendar, you become really good at planning your day by yourself. That is a grown-up skill, and now you have it!