What is the time difference between London and Greenwich mean?

Answer 1

At one time, the most accurate time update was the daily observation of when the sun was at its highest point in the sky as seen from the observatory at Greenwich, England. After the daily observation telegraphs would then be sent to other cities so they could synchronize their clocks. This "precise" time reference is what was known as Greenwich Mean Time (GMT) (mean is a synonym of average).

Today we use atomic clocks to accurately keep track of the passage of time. The name for the official standard by which time is measured around the world is Coordinated Universal Time (UTC). The time in any time zone can be expressed as an offset from UTC. For example, Pacific Daylight Saving Time in North America (PDT) is UTC - 7 hrs. or UTC-7, and Western Standard Time in Australia (WST) is UTC + 8 hrs. or UTC+8.

Because of the different ways at which they are arrived, Coordinated Universal Time and Greenwich Mean Time do not mean exactly the same thing, so it is no longer proper to define the time in a certain time zone by its offset from GMT.

The time in England, including London and Greenwich, is 1 hr. ahead of UTC from the last Sun. of March until the last Sun. of Oct. and is referred to as British Summer Time (BST). England is on GMT the rest of the year.

Answer 2

London time is the same as Greenwich Mean Time (GMT) during the winter months. However, during daylight saving time, London follows British Summer Time (BST), which is GMT+1.

Answer 3

universal time and zulu time

Answer 4

prime meridian.