The Queen’s birthday celebrates the monarch of a country. Different countries celebrate on different dates and is adopted by each country by royal proclamations or statute laws.
Her Majesty the Queen in the UK and Commonwealth territories is celebrated on different dates in June and does not coincide with the current Queens actual birthday, but as a celebration of her Official birthday. In the UK it is typically celebrated on the first, second, or third Saturday in June. Anguilla, Gibraltar, Montserrat, the Caiman Islands, and the Turks and Caicos Islands celebrate the holiday on the third Monday in June. Other Commonwealth realms and British overseas territories have chosen other dates.