Introduction to zero longitude and latitude: In 1884, astronomers from more than 20 countries around the world held a meeting in Washington, USA, and formally determined that the meridian passing through the observatory’s star instrument was the zero-degree longitude, and the east longitude was called east longitude, and the west longitude was called west longitude; Each is 180 degrees, and every 15 degrees is a time zone. The difference between adjacent time zones is one hour.