Queen's Official Birthday Events

William aged 3 and Harry 9 months 1985

The Queen's birthday is on 21st April but the official celebration is held in June- usually the second Saturday. The reason the official celebrations are not until June is that the chances of good weather are higher in the Summer. 

Yesterday most members of the Royal Family attended a Thanksgiving Service at St. Paul's Cathedral.

Today, the annual Trooping the Colour will take place. Let's hope little Princess Charlotte makes an appearance on the palace balcony!

The Trooping the Colour starts with Queen Elizabeth and members of the Royal Family travelling from Buckingham Palace, down The Mall to Horse Guards Parade in Whitehall.The ceremony is explained on the royal.gov.uk website:

What happens during Trooping the Colour?

Once The Queen has arrived at Horse Guard's Parade in Whitehall, she is greeted by a Royal salute and carries out an inspection of the troops, who are fully trained and operational soldiers wearing the ceremonial uniform of red tunics and bearskin hats.
The Queen used to attend on horseback herself, but in recent years has travelled by carriage.
After the military bands have performed, the escorted Regimental Colour, or flag, is processed down the ranks of soldiers. Over one hundred words of command are used by the Officer in Command of the Parade to direct the several hundred soldiers.
Once the Foot Guards have marched past The Queen, she rides back to Buckingham Palace at the head of the soldiers, before taking the salute again at the Palace from a dais. 
Her Majesty is then joined by other Members of the Royal Family on the balcony at Buckingham Palace to watch a fly-past by the Royal Air Force. A 41-gun salute is also fired in Green Park to mark the occasion. 

Horse Guards Parade