International Date Line Lesson for Kids: Definition & Facts

Instructor: Suzanne Rose

Suzanne has taught all levels PK-graduate school and has a PhD in Instructional Systems Design. She currently teachers literacy courses to preservice and inservice teachers.

Do you think it's possible to go back in time? In this lesson, you'll find out whether we can go back to tomorrow, and what the International Date Line has to do with what day it is on the Earth.

Is Time Travel Possible?

How'd you like to be able to go back to yesterday? Or maybe go ahead to tomorrow? We'd need to have a time machine to go back (or forward) for the whole day and unfortunately, they don't exist (yet!).

You CAN actually go back to yesterday or forward to tomorrow - but only for about a short time and only if you're in the right place on Earth! Let's find out where our days start and end.

The International Date Line

In the middle of the Pacific Ocean is an imaginary line that is called the International Date Line. It runs from the North Pole to the South Pole and is almost directly on the opposite side of Earth from the Prime Meridian, which is 0 degrees longitude. Remember, longitude lines are imaginary lines that run from north to south and divide the Earth into 360 parts. They can help tell you where you are in the Eastern or Western Hemisphere of the Earth.


The International Date Line was drawn over 130 years ago and is officially the line that separates two different days on the calendar! So, on one side of the line, it's Tuesday and on the other side of the line, it's Wednesday! If you stood on one side and then hopped over to the other, you could say you're sort of time traveling!

When you move to the west from the International Date Line, the date becomes one day later. Actually, it's impossible to jump back and forth across the line because it's in the middle of the ocean, and it's an imaginary line, so it's not really there!

Why an Imaginary Line?

A long time ago, before telephones and the Internet, and before planes and fast ships, people around the world didn't have much contact with each other. They could sort of 'tell time' by the Sun; when it was straight up in the sky, it was noon. As it became possible to talk to and visit people around the world with just a plane ride and people started doing business with others in other countries, we needed a way to agree about what the date and time would be everywhere on Earth.

Island of Kiribati

This led to the development of time zones (which divide the world into 24 sections, one for each hour of the day) and the International Date Line. Countries use UTC, or Coordinated Universal Time, so that the entire world agrees about what time it is.

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