It's good to be the queen. Especially because it apparently means you get not one, but two birthdays — every year, for all of time.Queen Elizabeth II was born on April 21, 1926 — which means that she turns 90 today. But her "official" birthday won't actually arrive until June. So why the double celebration?The reason dates back to 1748, when King George II was concerned that his annual birthday parade might be spoiled by undesirable November weather patterns. Instead of chancing it, George decided to combine his personal celebrations with the annual spring military parade, called Trooping the Colour.Since then, reigning royals have been given the option of an "official" birthday in the summer, coinciding with the Trooping the Colour festivities. Queen Elizabeth II opted in and celebrates her birthday on a Saturday in June, so that members of the public can enjoy the parade and events. According to The Telegraph, the queen will be spending today — her actual birthday — privately, though there will be a series of fun salutes in her honor at noon. Following tradition, she will appear on the balcony of Buckingham Palace along with other members of the Royal family after the Trooping of the Colour festivities end; this year, that parade and the queen's "official" birthday fall on June 11.