According to this
11:00 (precisely)
HM The Queen arrives on Horse Guards Parade to take the Royal Salute.
The Queen then reviews Her Guards riding slowly down the ranks of foot guards and cavalry in a carriage.
During the parade The Colour is Trooped through the ranks before the Foot Guards march past The Queen.
Then the Household Cavalry and Kings Troop Royal Horse Artillery rank past.
12:20
HM The Queen, at the head of Her Guards, returns up The Mall to Buckingham Palace.
12:20
HM The Queen, at the head of Her Guards, returns up The Mall to Buckingham Palace.
At the gates of Buckingham Palace HM The Queen dismounts from the carriage and mounts a dais to watch the parade march past in salute.
12:52
Kings Troop Royal Horse Artillery fire a 41 Gun Salute in The Green Park to celebrate The Queen's Official Birthday.
12:55 (approximately)
HM The Queen and other members of the Royal Family make a balcony appearance at Buckingham Palace.
13:00
Fly Past by the Royal Air Force