Queen Elizabeth II celebrates her ‘actual’ 91st birthday on 21 April.
After a lavish celebration for her 90th birthdays last year, which saw parties popping up all over Britain, 2017 will be a quieter affair spent with family.
She will appear on the balcony of Buckingham Palace on the day, according to tradition.
As the reigning monarch The Queen has two birthdays – her real one and her official birthday, which falls on 17 June.
The two-birthday tradition was started by King George II in 1748, and it’s all the fault of the Great British weather.
King George thought that it would be too cold for his birthday parade in November, when he was born, so he combined his birthday festivities with the annual Trooping the Colour parade in spring.
Queen Elizabeth II changed her official birthday from a Thursday to a Saturday so that the public could celebrate the occasion.
Elizabeth became Queen of England on 6 February 1952 following the death of her father, King George VI.
The then 25-year-old, christened Elizabeth Alexandra Mary, was staying in a remote part of Kenya when she received the news.
She immediately flew back home to Britain as Queen, where she was greeted by Prime Minister Winston Churchill.
Her coronation took place on 2 June 1953, and was broadcast on television for the very first time.
In September 2015, she became the longest-reigning UK monarch in history.