This is when George, Charlotte and Louis will have to start bowing to The Queen
So many royal rules, so little time.
Has anyone else noticed that Prince George and Princess Charlotte don't bow to the Queen?
Neither does Louis, but in fairness, he can't really even walk yet.
In fairness, they're children, but that does not make them exempt from this tradition.
According to Marlene Eilers Koenig, a royal historian, the young royals will be bowing very soon.
"Certainly by age five. The only person they will curtsy or bow to is the sovereign. A royal highness does not curtsy to another royal highness."
Prince George just celebrated his fifth birthday, and while we're yet to see a bow - we're sure he's practicing.
For the young Prince's birthday last year, he celebrated in the Caribbean with his family.
He also received a special commemorative coin from the royal mint to honour his fifth year.
The lovely Princess Charlotte is only three, so she has a couple of years until she's expected to curtsey to her Great-Gran.
And as for Prince Louis, we have quite a while to wait.
So there you have it!
Expect to see George and Charlotte bowing to their lovely Great Grandmother soon enough.