The Queen will mark it quietly and with sombre reflection but she will certainly pause to mark the passing of her father, George, 66 years ago.
For Queen Elizabeth II, the date of 6 February 1952 is not just the day her father died of lung cancer, but the moment her life changed completely and permanently.
Princess Elizabeth was in Kenya at the time, with her husband Prince Philip, at the start of a tour of the Commonwealth that the King was simply too ill to complete.
His daughter had left Heathrow airport a few days before as a princess, she returned suddenly as Queen.
There is no big anniversary this year – we’ve had the Silver, the Golden, the Diamond and – last year – the Sapphire Jubilee.
We’ve had the moment The Queen became this country’s longest serving Monarch – overtaking her great-great-grandmother Queen Victoria - as she did in 2015.
It’s just another year in a remarkably long reign.
There will be a gun salute in London at 1pm.
The Queen will now return from Sandringham, where her father passed away.
She has completed 66 years as this country’s Monarch and will now enter her 67th.