Breaking up a Day into Hours

Humans have been measuring time for thousands of years. A day is made up of twenty-four (24) hours. What is an hour? As far as your ability to tell time is concerned, an hour is made up of sixty (60) minutes. The twenty-four hours in every day are broken up into two sets of twelve hours. The first set of twelve is the AM period and the second set is the PM period. AM is from midnight to noon while PM is from noon to midnight.

Why do we use twelve hour amounts? It has to do with an old counting system that was based on the number twelve. We wound up with twelve months, hours, horoscope signs, and the number of donuts you might buy (a dozen). Although times may have changed and we now move towards metric systems of measurement, the twelves of the world will always be with us.

Hours Used in Measurement

The lifespan of some small insects is measured in hours. Hours are great for business. People go to work for eight hours a day. They go to lunch for one hour a day. They might even have a commute for one hour a day. Hours divide our days into bite-sized pieces that we all understand. You have probably been told you need eight hours of sleep or that you can only watch two hours of television each day. Hours are everywhere. They may our daily schedules possible.

Hours are also great when you need to round off times. Let's say your drive to work takes you fifty-five (55) minutes. You don't tell people fifty-five minutes. You round up to an hour because it's easier to understand and shorter to say. If you worked for eight hours and twelve minutes, you would probably round off the value to eight hours. People don't have to think when they hear eight hours. For casual conversation, eight hours and twelve minutes is too detailed.

Common Amounts of Time:
Time at the gym each day: 1 Hour
Length of a movie: 2 Hours
Nightly prime-time television: 3 Hours
Time difference between Los Angeles and New York: 3 Hours
Time your food spends in the small intestine: 4 Hours
Time for sleep each night: 8 Hours
Length average work day: 8 Hours
Length of a day: 24 Hours
Lifespan of Gastrotrich (shortest lifespan): 36 Hours
Length of the weekend: 48 Hours

Details to Remember

- There are 24 hours in a day.
- There are about 12 hours of light and dark each day.
- There are 60 minutes in each hour.
- A clock shows time for 12 hours and then repeats.

Related Activities

Date and Time Activity Learning to Read Analog and Digital Clocks
- Play Activity

Date and Time Activity Telling Time on a Clock
- Play Activity


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