Trooping the Colour is a ceremonial event performed every year on Horse Guards Parade in London, United Kingdom, by regiments of Household Division, to celebrate the official birthday of the British sovereign, though the event is not necessarily held on that day. It is also known as the Sovereign's Birthday Parade. Similar events are held in other countries of the Commonwealth. In the UK, it is, with the State Opening of Parliament, the biggest event of the ceremonial calendar, and watched by millions on TV and on the streets of London.