Toby Melville - WPA Pool/Getty ImagesAlthough the milestone day isn't until tomorrow, April 21, Queen Elizabeth will kick off her 90th birthday today and continue the celebrations over the next 48 hours.
This morning, she began the festivities by joining alongside Prince Philip and visiting a Royal Mail sorting office in honor of a new special birthday stamp featuring the Queen as well as to celebrate the postal office's 500th anniversary. Shortly thereafter, she and Philip opened a new bandstand where children sang and performed in front of them.
Later this evening we can also look forward to new, official photos of Her Royal Highness, which will be released at 7:01 p.m. EST.
On Thursday, Queen Elizabeth and Prince Philip will have a walkabout in Windsor Castle to meet and greet well-wishes. They will also join other 90-year-olds at Windsor Guildhall to cut and share a birthday cake.
She will then light the first of over 1000 beacons to be lit across the United Kingdom, during which her son, Prince Charles, will give a short speech.
Aside from her royal visitations, BBC will also air a documentary titled Elizabeth at 90: A Family Tribute on Thursday, which will feature unseen home movies as well as appearances by many other royals.
Several gun salutes in honor of the Queen's birthday will take place throughout the day: Hyde Park at 7 a.m. EST as well as Windsor Great Park and a the Tower of London at 8 a.m. EST.