Time
Time is a big part of our everyday lives! It helps us plan what we do, keep our schedules on track, and remember special moments. Learning about time lets us answer fun and useful questions like:
- What time does my favorite movie start?
- How long will it take to drive to the beach?
- When is the next school holiday?
- When did dinosaurs roam the Earth?
Units of Time
A unit of time is a way to measure how long something takes. We use different units depending on what we’re timing!
Definition Common Units of Time
Here are the units we use most often:
- Seconds (s) – for quick things, like a race.
- Minutes (min) – for short activities, like a break.
- Hours (h) – for longer events, like school.
- Days (d) – for full days, like a weekend.
- Weeks (wk) – for several days, like a vacation.
- Months (mo) – for parts of a year, like summer.
- Years (yr) – for long periods, like your age.
Example
Which unit of time would you use to measure how long it takes to run 100 meters?
We use seconds because running 100 meters is a quick event.
So, the unit is seconds (s).
So, the unit is seconds (s).
Converting Units of Time
Definition Converting Units of Time
To change between units of time, use these facts:
- 1 minute = 60 seconds
- 1 hour = 60 minutes
- 1 day = 24 hours
- 1 week = 7 days
Method How to Convert
- Use multiplication to go from a bigger unit to a smaller one (like minutes to seconds).
- Use division to go from a smaller unit to a bigger one (like minutes to hours).
Example
Convert 2 minutes to seconds.
Since 1 minute = 60 seconds:$$\begin{aligned}[t]2 \, \text{min} &= 2 \times 60 \, \text{s} \\&= 120 \, \text{s}\end{aligned}$$So, 2 minutes is 120 seconds.
Since 1 minute = 60 seconds:$$\begin{aligned}120 \, \text{s} &= 120 \div 60 \, \text{min} \\&= 2 \, \text{min}\end{aligned}$$So, 120 seconds is 2 minutes.
24-Hour Time Format
Definition 24-Hour Time Format
The 24-hour time format is a way to tell time without using AM or PM. It counts all 24 hours in a day, from 00:00 (midnight) to 23:59 (almost midnight again).
Example
Write 6:15 PM in 24-hour time.
Since 6:15 PM is 6 hours after noon (12:00):$$\begin{aligned}[t]6:15 \, \text{PM} &= 12 \, \text{h} + 6 \, \text{h} + 15 \, \text{min} \\&= 18 \, \text{h} + 15 \, \text{min} \\&= 18:15\end{aligned}$$So, 6:15 PM is 18:15 in 24-hour time.
Reading Clock
Method Reading Clock in 5-Minute Intervals
- Hours: The little hand points to the hour. Look at the number it’s on. If it’s between two numbers, choose the smaller one.
- Minutes: The big hand points to the minutes. Look at the number it’s on. Each number means 5 minutes. For example: 1 is 5 minutes, 2 is 10 minutes, 3 is 15 minutes, ..., 12 is 0 minutes (o’clock).
Example
What time does this clock show?
Morning
Morning
- The little hand points between 7 and 8. We pick the smaller one, so it’s 7. That’s the hour.
- The big hand points to 7. Each number is 5 minutes, so 7 times 5 is 35 minutes.
- It’s morning, so the time is 7:35 in the morning.