Why Does Queen Elizabeth Have Two Birthdays?

This weekend, Australia -- excluding WA and Queensland -- is celebrating the birthday of our monarch Queen Elizabeth II.

While the June long-weekend has been the only date the Queen's birthday has been celebrated in most Australians' living memories, Queen Elizabeth was actually born on April 21st, 1926.

So why do Australia and the rest of the Commonwealth celebrate her birthday almost two months later?

Associate Professor at Flinders University Giselle Bastin who has spent years researching the British Royal Family, said while the birth of the monarch has always been celebrated, centuries ago it was commemorated on their actual birthday.

Queen Elizabeth, Prince Charles, Princess Anne & Prince Philip Royal Family approximate date 1953.

Bastin told 10 daily the monarch's birthday has been celebrated in Britain since 1748, and in Australia, the tradition continued when colonisers first arrived in the country in 1788.

According to Bastin, there are two main theories around when and why the celebration date was changed to June.

Some people believe the change occurred in 1936 when the Queen's grandfather, King George V died. George's birthday was in early June and some people believe that the official sovereign's birthday date was changed around that time in his honour.

The future Queen Elizabeth II waving from the balcony of Buckingham Palace in London, with her younger sister Margaret and her grandparents King George V and Queen Mary, on the occasion of their Silver Jubilee, 6th May 1935. Photo: Central Press/Hulton Archive/Getty Images.

The other theory is that the June holiday coincides with the traditional Trooping of the Colour which marks the monarch's birthday celebrations every year. Bastin explains that some people believe it was King George's father King Edvard VII who changed the date.

Edward was born in November, during the winter season in Britain, and one theory claims Edward moved the date of the Trooping of the Colour to June in order to take advantage of the summer months in Europe.

1902: Edward VII King of Great Britain and Emperor of India (1841 - 1910) wearing state robes for his coronation. Photo: by Hulton Archive/Getty Images

Regardless of the date change, however, the annual parade has remained a significant event that marks the sovereign's birthday.

"It's always held on the unofficial date and people are often surprised that she has her birthday in April because they just think she's being greedy," Bastin joked.

Similar parades are held in Australia, Canada, Ghana, and other Commonwealth nations on the unofficial date as well in celebration.

The trooping of the colour is one of the most important events in the Royal calendar. PHOTO: Getty Images.

"It's possibly the most important event of all for the Royal Family, and that's why the whole family turns up on the balcony," Bastin explained.

The 2019 parade held on Saturday also saw Meghan Markle's return to Royal duties, with the Duchess of Sussex making her first public appearance since giving birth to baby Archie.

READ MORE: Meghan Markle Makes First Royal Appearance Since Birth Of Baby Archie

Will The Date Ever Change?

Bastin said that while any future monarch is within their right to change the official date, it's unlikely they would choose to do so.

"I think Charles won't change that and eventually not William either, because it's so much a part of the official summer calendar," Bastin said.

"I can't see him saying 'no, you can't have the day off anymore.'"

But while the future head of the Commonwealth might not choose to change the date themselves, Bastin said it's likely the public holiday will be scrapped from the Australian calendar if we were to become a republic.

Queen Elizabeth ll smiles amongst Australian flags being waved by the crowd after the Commonwealth Day Service March 13, 2006 in Sydney, Australia. PHOTO: Getty Images

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"I would say it will and that will lead to discussions about perhaps thinking with the Queen's birthday gone and with the Australia day date, as we've seen is certainly a matter for debate for some people, so I think that it might be the catalyst for a discussion to Australia finding a whole new day for itself."

The Queen's birthday is marked with a public holiday on Monday June 10 for all states and territories excluding WA, who celebrate on September 30 and Queensland who celebrate on October 7 -- to avoid clashes with other public holiday dates.

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