Explanation

The degree of the Greenwich meridian in England is 0° 0' 0", or the Prime Meridian: 

It is an imaginary line that runs through Greenwich, a borough of London and ends at the North and South poles.  

It was last established in 1851

Greenwich is an area in south-east London, England

It lies on the south bank of the River Thames in the historic county of Kent.

It is used as the reference for Greenwich Mean Time (GMT).

Greenwich is famous for calculating the time for all countries.

The Greenwich meridian, also known as the prime meridian, passes through the following countries:

• England
• France
• Spain
• Algeria
• Mali
• Burkina Faso
• Togo
• Ghana 
• Antarctica