Greenwich
Greenwich, located in South East London is renowned for its maritime history and for giving its name to the Greenwich Meridian (0° longitude) and Greenwich Mean Time. The town became the site of a royal palace, the Palace of Placentia from the 15th century, and was the birthplace of many in the House of Tudor, including Henry VIII and Elizabeth I. The town became a popular resort in the 17th century and many grand houses were built there, such as Vanbrugh Castle, built in 1717. The maritime connections of Greenwich were celebrated in the 20th century, with the siting of the Cutty Sark and Gipsy Moth IV next to the river front, and the National Maritime Museum in the former buildings of the Royal Hospital School in 1934.
The Greenwich meridian and Greenwich Mean Time (GMT)
As the United Kingdom grew into an advanced maritime nation, British mariners kept at least one chronometer on GMT in order to calculate their longitude from the Greenwich meridian, which was by convention considered to have longitude zero degrees (this convention was internationally adopted in the International Meridian Conference of 1884). Note that the synchronization of the chronometer on GMT did not affect shipboard time itself, which was still solar time. But this practice, combined with mariners from other nations drawing from Nevil Maskelyne’s method of lunar distances based on observations at Greenwich, eventually led to GMT being used worldwide as a reference time independent of location. Most time zones were based upon this reference as a number of hours and half-hours “ahead of GMT” or “behind GMT”.