Information copied from the internet:
‘The bright red Time Ball on top of Flamsteed House is one of the world’s earliest public time signals, distributing time to ships on the Thames and many Londoners. It was first used in 1833 and still operates today.
Each day, at 12.55, the time ball rises half way up its mast. At 12.58 it rises all the way to the top. At 13.00 exactly, the ball falls, and so provides a signal to anyone who happens to be looking. Of course, if you were looking the wrong way, you had to wait until the next day before it happened again.
The Time Ball drops at 13.00 GMT during the winter months and 13.00 BST during the summer. Please note: the time ball will not be run if the weather is too windy.
What did people do before there was a time ball?
Only the richest people could afford to buy clocks and watches of their own. Most people relied public sundials to tell the time. This led to different local times across the country, with clocks on the eastern side of the country about 30 minutes ahead of those in the west.
The difficulties created by everyone using their own local time eventually led to the creation of Standard Time based on the Prime Meridian at Greenwich.’