[goosedragons]

We already solved the birthday celebration problem. The Queen's official birthday in Canada is May 24th. Charles' official birthday in Canada will be May 24th. We just decided at some point the best monarch's birthday to celebrate is Queen Victoria and have stuck with it.

[Ichthypresbyter]

The Dutch continued celebrating Queen Juliana's birthday (April 30th) as their national day when Queen Beatrix succeeded her, as they didn't want to move an event which is traditionally celebrated outdoors to January.

Beatrix was succeeded by King Willem-Alexander, who was born on April 27th- so the national day moved to his actual birthday. April 30th is now known mainly for confused tourists expecting a party that happened three days earlier.