Why Are There Time Zones?

Lesson Plan - Get It!

Audio:

These are great questions! It is time to explore time zones.

Our earth is a sphere that rotates around the sun, resulting in a 365-day-long year. It also spins on an axis, resulting in a 24-hour day, simultaneously spinning and rotating.

Look at this silent video to see how it happens.

Depending on where you live on earth, your home is in a particular time zone.

There are currently 24 time zones worldwide (2023). Each time zone is one hour ahead of or behind the zone next to it.

For instance, if you live in Denver, Colorado, you are in the mountain time zone. This is one hour ahead of the Pacific time zone and one hour behind the central time zone.

This means that when it is noon in the central time zone, it is 11:00 a.m. in the mountain and 10:00 a.m. in the Pacific time zone.

• Why do you think there are time zones on earth?

Think about the video showing the earth's and the sun's relationship. This may help you with this answer.

• When thinking about how the earth rotates on its axis, what happens to the sunlight as it turns?

Consider that the sun does not move, but the earth spins around, and as one part of the earth has sunlight, the opposite side of the earth is facing away from the sun, making it nighttime.

Check out this image of our rotating earth.

Knowing all 24 of the time zone names is not necessary, but knowing the names of the time zones on your continent is important.

Find your home zone and the zones that make up your continent or country on this Time Zone Map. Familiarize yourself with the names of the time zones.

As an interesting side-note, the names of the time zones in one country are different than those of a country with the same latitude.

For example, the eastern time zone of the United States is the same latitude as the western coast of South America, and the time zone there is called PET (Peru time).

This makes sense because the U.S.'s eastern time zone is on the country's eastern side, and the PET is on the western side of South America. It surely wouldn't make sense to call it the Eastern time zone in South America!

All 24 time zones worldwide are in relation to the UTC, the Coordinated Universal Time. This is the time zone in countries like Spain, the United Kingdom, Mali, Ghana, and much of the north and south Atlantic Ocean.

This is the time zone that is the standard by which the world regulates clocks and time. This concept was not adapted until 1972!

But wait, there's more!

There are two times a year when the time on the clock is changed, called daylight saving time (DST) or summer time.

Countries along the equator have a 12-hour day regardless of the time of year, so they do not usually participate in DST, but MOST other areas of the earth participate in daylight saving.

The inception of the idea came from Benjamin Franklin. He believed that the sunlight in the summer months was put to better use in the evenings than in the mornings, so in the springtime, clocks are moved forward by one hour.

Since there are longer periods of sunlight in the summer, this extra hour in the evenings gives farmers more time to work. It also creates less of a need for electricity because more people enjoy the warmer weather outside than in their homes.

Proponents of DST believe it saves on energy costs.

Clocks are set back one hour in the fall because the belief is that it returns time to its original setting. Daylight saving time begins at 2:00 a.m. on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November.

• Does your country participate in DST?

You saw in the opening video what happens when some counties in some states in the United States decide not to participate in daylight saving time.

In the Got It? section, research locations that do not participate in DST and discover why not.