Prime Meridian Day - November 1
(Last Updated On: December 15, 2022)


On November 1st, Prime Meridian Day celebrates the imaginary line that divides Earth into the Eastern and Western Hemispheres. It’s also a time to learn more about the prime meridian.

You have probably looked at a map or globe and noticed lines of latitude and longitude. These lines were developed to make it easier to find certain places. We use lines of latitude to give a coordinate that is north or south of the equator. Lines of longitude are used to give coordinates east or west of the prime meridian. A Greek astronomer named Hipparchus first used these lines of latitude and longitude to find a specific location. Hipparchus lived from 190 to 120 BC.

The prime meridian (which is 0 degrees longitude) could have been set anywhere. However, for many years, governments of different countries disagreed on the prime meridian’s location. For example, mapmakers in France marked the prime meridian in Paris while the Chinese government published maps with 0 degrees longitude going through Beijing. It wasn’t until 1884 that governments from various countries agreed on Greenwich, England, as the prime meridian’s official location.

Along with making travel easier, the prime meridian serves a few other purposes. For instance, it sets the Coordinated Universal Time. Every country and region measures its time zones according to the Coordinated Universal Time. There are a total of 24 time zones in the world. One more reason for the prime meridian is that it helps establish the International Date Line. This line is located at 180 degrees and marks the halfway point for the Earth. When you go west past the International Date Line, you add a day. When you go east from the International Date Line, you subtract a day.

HOW TO OBSERVE #PrimeMeridianDay

Schools, mapmakers, and geographers hold special events on this day to educate the general public on the prime meridian. It’s also a fun day to learn more about maps, globes, and lines of latitude and longitude. To participate:

  • Have a contest with friends to see who can find the most places on a globe using lines of latitude and longitude.
  • Learn more about the Royal Observatory in Greenwich, England.
  • Find out what time it is in different parts of the world.
  • List countries in the Western Hemisphere and also in the Eastern Hemisphere.

Share this day on social media with #PrimeMeridianDay.


In October of 1884, U.S. President Chester Arthur called for an International Meridian convention. It was here that representatives from 25 countries agreed on the official location of the prime meridian. They chose to set the Royal Observatory in Greenwich, England at 0 degrees longitude. Despite this agreement, it took several years for every country in the world to agree on the official location for the prime meridian. In recent years, Prime Meridian Day has been observed each year on November 1st.


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