Queen's Birthday

We are on a long weekend due to "Queen's Birthday" coming on Monday.

As I was writing an article for my Japanese blog, I suddenly wondered which Queen's birthday celebration it is for.

Wikipedia is a handy tool for any research as you all know.
All you have to do is to type in the keyword and there, there...you get all you want to know...or not???

The result of my wiki-search was shocking.
As usual, I was mumbling in front of PC
Uh, huh...uh, huh...Huh?

Queen's official birthday is actually on April 21, so this celebration is definitely not for her birthday.
So I read on...

According to Wikipedia, Queen's Birthday is NOT queen's birthday after all.
This day originally celebrated the birthday of George V, whose birthday was 3-June. The tradition began in 1788 to celebrate the birthday of the King of England.
However, another source says it was George III(Queen's Grandfather)'s birthday it celebrated, whose birthday was 4-June.

So why was it named 'Queen's Birthday', but not 'King's Birthday'?
That was the question I didn't get the answer.

Wikipedia notes that Queen Elizabeth II's coronation was on 2-June.
Would the celebration have anything to do with it? - I doubt that.
By the way, Elizabeth I was born on 7 Sept 1533.
(You can see that I rely heavily on Wikipedia...although I don't know how accurate the information is.)

In UK her birthday is celebrated on 1st, 2nd and 3rd Saturday in June as well as on her own birthday.

I couldn't get the answer I wanted, but I think Elizabeth II is very fortunate to have her birthday celebrated so many times a year and receive a lot of prezzies!!!