The Queen marks her official birthday this month - but why does she have two birthdays?
The Queen turned 90 on April 21. But she also has an official birthday on Saturday, the day after her right royal husband's 95th birthday.
Confused? You will be!
It's all down to our inclement weather. Since 1748 the monarch's official birthday has been marked by Trooping the Colour parade - usually held on the king or queen's actual birthday.
But Edward VII, who reigned from 1901 to 1910, was born in November. He celebrated officially in May or June because there was less chance of it being cold and drizzly during the outdoor event.
The monarch after Edward VII - George V - helpfully had a birthday in June. But The Queen's father, George VI, whose birthday was in December, reintroduced the tradition of an official birthday, which Elizabeth II has continued.
Is her official birthday always on a Saturday? It is now.
George VI had his official birthday on the second Thursday of June. In 1959, after several years on the throne, The Queen changed it to the second Saturday for convenience.
It can now be on either the first or the second, sometimes the third Saturday of the month, and is marked by Trooping the Colour carriage and horse procession in central London and a fly-past over Buckingham Palace.
The Queen's Birthday Honours List is also announced, the Union flag flown from government buildings and gun salutes fired at noon.
What does she usually do on her actual birthday? HRH gets to spend it privately - except when duty beckons or it is a milestone celebration.
On her 90th, she carried out a birthday walkabout in Windsor and in the evening lit a beacon before joining her family for a lavish black tie dinner at Windsor Castle.
Aides do try to give the Queen a break on her birthday from famous red boxes containing state papers.
And on her official birthday? It's a busy affair this year.
There is a weekend of special events, starting with a service of thanksgiving at St Paul's Cathedral on Friday, Trooping the Colour on Saturday and street party on The Mall on Sunday.
Does the Queen actually have more than two birthdays? Technically, yes.
A number of Commonwealth realms celebrate the occasion at different times of the year. Most of Australia, where the Queen is head of state, has a public holiday on the second Monday in June to mark her birthday, while in western Australia it is celebrated at the end of September or beginning of October. In New Zealand, it's the first Monday in June.
In Canada, the Queen's official birthday is on Victoria Day - the Monday before May 25, the day after Queen Victoria was born.
What will happen in the future? The Prince of Wales's birthday is in November, so he is likely to continue the tradition if and when he is king.
Who else has two birthdays? Paddington, the marmalade-loving bear from deepest, darkest Peru - on June 25 and December 25.
His adopted family The Browns agreed bears "just like the Queen" have two birthdays every year.