Almost two months after the Queen turned 91, Her Majesty today celebrates her official birthday, during which she is joined by other members of the Royal Family at the Trooping the Colour parade.
Here's everything you need to know about the Queen's birthday.
The Queen has two birthdays
Yes. The Queen celebrates her birthday twice each year - once on the anniversary of the day she was born, April 21, and on an "official" birthday in June, which this year falls on Saturday 17th June.
So why exactly does the Queen have two birthdays?
It is a tradition that was started by George II in 1748 and is owes its origins to the ageless problem of the British weather.
George was born in November, and felt the weather would be too cold at that time of year for his annual birthday parade.
So instead, he combined his birthday celebration with an annual spring military parade known as Trooping the Colour, in which regiments displayed their flags or "colours" so soldiers would be familiar with them.
It is a tradition that has continued to this day. All British sovereigns are given the option of having an "official" birthday, and because the Queen's real birthday is on April 21, she has stuck with the tradition of celebrating in June.
Otherwise known as The Queen's Birthday Parade, the Queen inspects soldiers from the Household Division. It takes place on Horse Guards Parade behind Whitehall, and is televised live by the BBC.
Why is her official birthday on a Saturday?
During the early part of her reign the Queen's official birthday was on a Thursday, but it later changed to a Saturday in June so that more members of the public could enjoy it.
The Queen usually spends her birthday privately, but the occasion is marked publicly by gun salutes at noon: a 41 gun salute in Hyde Park, a 21-gun salute in Windsor Great Park and a 62-gun salute at the Tower of London.