Updated: June 2, 2022 2:26 PM EDT | Originally published: April 20, 2018 1:04 PM EDT

The first week of June is set to be a big week for Queen Elizabeth II, as she celebrates both her Platinum Jubilee—70 years on the throne—on Jun. 1 and her official birthday on Jun. 2. Britons will get to enjoy a public holiday to mark the Jubilee, and a host of pageants, concerts, and parades will be held to mark the two occasions.

But, the Queen’s actual birthday was in April, when she turned 96. As always, Her Royal Majesty not only observes the anniversary of her birth, but also her official birthday as monarch.

Here’s why the Queen has two birthdays.

Why does the Queen have two birthdays?

Princess Elizabeth Alexandra Mary was born to the Duke and Duchess of York—later King George VI and Queen Elizabeth, The Queen Mother—on Apr. 21, 1926, making Apr. 21 her real birthday. However, when she became queen in 1952 following her father’s death, she also began celebrating her official birthday.

Celebrating an official birthday as monarch is a practice that started more than 250 years ago in 1748 when King George II decided that he wanted a better chance of good weather on his birthday than his November birth date afforded, according to the BBC. The King solved this problem by combining his birthday celebration with an annual military parade called Trooping the Color that took place each summer, beginning the double birthday tradition.

Since then, the second Saturday of June has become the usual date of the British monarch’s official birthday, though that isn’t the case in 2022.

Read More: Parades, Pageants, and Afternoon Tea: The History of Britain’s Royal Jubilee Celebrations

How will the Queen celebrate her real birthday?

Queen Elizabeth typically celebrates her real birthday with an intimate family gathering. This year, she marked the occasion at her country estate, Sandringham, staying in Wood Farm cottage—which was a favorite of her late husband, Prince Phillip.

As a public acknowledgement of the milestone, there were several midday gun salutes in cities across the U.K.—with 41 in Hyde Park and 62 at the Tower of London. The royal military band played a rendition of “Happy Birthday” at Windsor Castle.

The palace released an official photograph of the Queen for her birthday, which showed the monarch standing with two ponies at Windsor Castle, to reflect her lifelong love of horses.

Read More: As Queen Elizabeth II Marks Her Platinum Jubilee, Who Is the Longest Reigning Monarch?

What about the Queen’s official birthday?

The Queen’s official birthday would have fallen on Jun. 11 this year, the second Saturday of the month, as is the custom. But the day has been brought forward to Saturday, Jun. 2 to coincide with the Platinum Jubilee celebrations marking seven decades on the throne.

Alongside the other spectacular events scheduled for the Royal Jubilee—including a music and arts pageant in the capital and a concert at Buckingham Palace—the Queen’s official birthday will be marked with the Trooping the Color parade. The impressive spectacle—which begins and ends at Buckingham Palace—features hundreds of soldiers, horses, and musicians.

As the Queen has suffered recent mobility issues, it’s unclear whether she will participate in the procession with other members of the royal family. She is expected to appear on the Buckingham balcony as Royal Air Force planes perform an aerial display above the palace grounds.

This story was originally published in 2018 but has since been updated, including in 2022, to reflect the Queen’s official birthday this year.

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Write to Megan McCluskey at megan.mccluskey@time.com.

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