Prime Meridian Day 2025: Date, History, Activities, Facts about Time Zones

Prime Meridian Day 2025: Every year on November 1, people celebrate Prime Meridian Day. The big Airy Transit Circle telescope at the Royal Observatory in Greenwich, England, was used to describe the prime meridian in 1884. In 1850, Sir George Biddell Airy, the seventh Astronomer Royal, created the telescope that is still used today. The markers on the Airy Transit Circle marked 0° longitude. Today, we honor the prime meridian and all the things it did, like splitting the Earth into the Eastern and Western Hemispheres and setting up the world’s time zones.

HOW PRIME MERIDIAN DAY CAME TO BE

On October 1, 1884, President Chester A. Arthur of the United States hosted this event in Washington, D.C. The meeting was called to choose the official longitude of 0° and set up global time zones. This point is also known as the prime meridian. There were more than 41 participants from 25 different countries. Twenty-two of the countries that were there voted in favor of Greenwich. France and Brazil did not vote, and Haiti voted against it.

The world did not have a standard prime meridian before the meeting. Since lines of longitude are made up, many places were thought to be at 0° longitude. English Greenwich was named the world prime meridian on October 13. It is held every year on Prime Meridian Day to honor the event.

In the Greenwich Observatory, the prime meridian went through the middle of a transit device. The telescope changed its name to the Royal telescope, Greenwich over time. After the Second World War, the observatory was moved to Hailsham, East Sussex, even though Greenwich was still where the prime meridian went. In the end, the Hailsham site became known as the Observatory Science Center. After some time, the Royal Observatory moved back to Greenwich.

The International Date Line is in the Pacific Ocean at 180° longitude, as agreed upon in the treaty at the International Meridian Conference. There are many meridians, with a time change of one hour between each one every 15°. But some countries don’t follow the rule about changing the time. China, for instance, only has one time zone, even though it has five lines going through it.

BEST THINGS TO DO ON A MERIDIAN DAY

Check out the telescope

To find out more about the prime line, go to Greenwich’s Royal Observatory. To get the full view, you can also visit Hailsham’s Observatory Science Center.

Check out the world’s time zones.

It’s always fun to learn. Learn about the world’s time zones and make note of the differences between them. It could be useful at quiz night, you never know.

Find out where you are.

Get the exact location of where you live, work, or go to school. If someone asks for your home, this could be a funny answer.

5 AMAZING FACTS ABOUT TIME ZONES

• Antarctica doesn’t have a set time zone because not many people live there.
• Twelve months of the year, the world’s poles have nonstop sunshine for six months and nonstop darkness for the other six months.
• The country with the most time zones is France. The US and Russia are very close behind, each with eleven.
• France is an hour behind Greenwich Mean Time, even though the prime meridian goes through the country.
• The IERS Point of View Meridian is the current meridian that most people use.

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PRIME MERIDIAN DAY DATES

Year	Date	Day
2023	November 1	Wednesday
2024	November 1	Friday
2025	November 1	Saturday
2026	November 1	Sunday
2027	November 1	Monday