Today on bbc.com/news I found this article about the queen making her first public appearance since coronavirus:
The monarch spent her birthday on 21 April in lockdown with Prince Philip.
A number of annual events that mark the occasion had to be cancelled due to the pandemic - including Trooping the Colour, which celebrates the monarch's official birthday in June.
How is the Queen's "official birthday" in June if her birthday is on 21 April? What's an "official birthday"?