Timezone: London, United Kingdom

London is the home of the Prime Meridian and the historical origin of Greenwich Mean Time (GMT). For over a century, London time was the absolute reference point for the entire British Empire and, eventually, the world.

From Solar to Railway Time

Before the 1840s, London kept its own local solar time. However, the rise of the Great Western Railway made this impossible to manage. In 1847, the Railway Clearing House decreed that GMT should be used across all stations. By 1852, time signals were being sent via telegraph from the Royal Observatory in Greenwich to the rest of the country.

The Introduction of DST

During World War I, to save fuel and provide more daylight hours for workers, the UK introduced British Summer Time (BST). This shifts London from GMT (UTC+0) to BST (UTC+1) between March and October.

The Standard Today

Today, London remains a global hub for finance and technology. While UTC has replaced GMT as the precise scientific standard, the term "GMT" is still used colloquially across the UK to refer to the winter timezone.

Conclusion

London’s relationship with time is one of the most significant in human history. It is the place where local time first became global time. On the Epoch Clock, London sits at the zero-offset, the anchor for the count of seconds.