It turns out there's a special meaning behind Prince Louis' christening date ...

It's an exciting day today!

Because later tonight we will have our first look at the Cambridge's family of five all together when Prince Louis is christened.

Kensington Palace announced last month that Prince Louis' christening will take place at the Chapel Royal of St. James’s Palace in London.

The private 45-minute ceremony will likely be a small and intimate affair, with the Duke and Duchess of Cambridge previously only inviting 22 people to Prince George's christening and 30 guests to Princess Charlotte's.

But what makes the occasion extra special is the date.

On July 9, 1947, the then Princess Elizabeth announced her engagement to Philip Mountbatten, now known as Prince Philip.

Which makes the christening the sweetest tribute to Her Majesty.

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The venue of the royal tot's christening, also has a profound significance to Prince William, as his late mother, Princess Diana's coffin was placed at the palace's altar before her funeral at Westminster Abbey in 1997.

There's still no word on who Louis' godparents will be, but that's typically revealed at the ceremony.