The Greenwich Meridian is quite literally the place where time begins and time began. Every new day, year and millennium begins at the stroke of midnight on the Prime Meridian Line. This line accurately tells us where on earth the measurement 0 degrees longitude can be found. The line which circles the earth through the south and north poles has been used since the 19th Century as a way of standardising time around the world with all time zones being measured in hours before or behind Greenwich Mean Time. This is one of Greenwich's most visited attractions.