Today is the Queen's official birthday, despite the fact she was born in April.
It's a tradition that goes back to 1748 and is all about trying to make sure the weather is better for outdoor celebrations.
The Queen has two birthdays - her real one - on 21 April, as she was born on 21 April 1926.
Then a second one - the official celebration - on the second Saturday of June.
So why does the Queen have two birthdays, and how does she celebrate them?
In the past, official celebrations to mark a King or Queen's birthday in the UK have been held on a day that isn't their actual birthday.
The double birthday tradition was started more than 250 years ago by King George II in 1748.
He was born in November, which is not known in the UK for its good weather.
But King George wanted it to be possible to have a big public celebration - and November wasn't the time do it.
So, given that his actually birthday wouldn't be a good time of year for a birthday parade, he decided to combine it with an annual military parade in the summer, when the weather would hopefully be nice.
And so this is where the tradition of an official, public summer birthday for the monarch began!
The Queen usually spends her actual birthday with her family.
There is usually 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 on April 21 but they have been cancelled this year because of the coronavirus pandemic.
A Buckingham Palace official said the monarch had decided it would not be appropriate at this time.
It is believed to be the first time in her 68-year reign that it hasn't happened.
The Trooping the Colour parade marks her official birthday and usually takes place in June, but that has also been cancelled this year.
It is only the second time in her 68-year reign that the parade has not gone ahead.
A small ceremony with Welsh Guardsmen and military musicians will take place at Windsor Castle instead.
Trooping the Colour has marked the official birthday of the British monarch for over 260 years.
Over 1400 soldiers, 200 horses and 400 musicians take part in the event, so it's quite a spectacle!
Lots of members of the public waving flags and wearing Union Jacks usually fill the Mall outside Buckingham Palace to watch it.
On the day, normally a big parade starts at the Queen's official residence - Buckingham Palace - before moving along the Mall to Horse Guards Parade at Whitehall, near to Downing Street, and then back again.
Then it's traditional for the royal family to travel down the Mall as part of the ceremony, and gather on Buckingham Palace's balcony to greet well-wishers and watch RAF planes perform an aerial display for the occasion.