What is the Greenwich Mean Time

Greenwich Observatory. G.M.T. (Zulu)- Officially
Wikimedia Commons by Ron Hann

Greenwich is a metropolitan borough in London, and is situated on ricer Thames. It is famous for its royal observatory, from which the international standard time is taken. Greenwich became a royal borough in 2012.

The Greenwich meridian, that is the 0 degree longitude is taken from it. In other words it is from Greenwich that the degree of longitudes are reckoned with us. 

Since the globe is divided into 360 degrees, longitudes and as the earth goes round its axis in twenty four hours, so 15 degree longitude = one hour. The time is increased or decreased according to the position or longitudes.