when did the two grand lodges actually unite

The formal union between the Antient Grand Lodge and the Premier Grand Lodge (the Moderns) took place on St. John's Day, December 27, 1813 13.

Preliminary steps toward the union began as early as 1801, though an abortive attempt occurred in the Antient Grand Lodge in 1797 2. In 1809, the Earl of Moira warranted the Lodge of Promulgation specifically to prepare for the union 2. On September 1, 1813, the Duke of Kent was appointed by the Antients to a committee alongside Deputy Grand Master Harper and Past Deputy Grand Masters Perry and Agar 1. This committee held conferences with the Duke of Sussex and three of his Grand Officers, leading to the drafting of the Articles of Union at Kensington Palace 1.

The Articles of Union were solemnly ratified by both Grand Lodges during their Quarterly Communications early in December 1813 1. The formal assembly to execute the union then convened on December 27, 1813, at Freemasons' Hall in London 13. During the ceremony, both Grand Lodges entered side by side, and the Articles of Union were read 13. The Duke of Kent addressed the assembly and nominated his brother, the Duke of Sussex, who was unanimously elected Grand Master of the new United Grand Lodge of England 13.

Among the terms established by the union, Article II declared that pure Ancient Masonry consists of three degrees—Entered Apprentice, Fellow Craft, and Master Mason—including the Supreme Order of the Holy Royal Arch 23. To reconcile the differing practices, each Grand Lodge appointed a committee of nine expert Master Masons to serve in the Lodge of Reconciliation, which instructed brethren in the combined forms of both systems 12. The relative priority of lodge numbers between the two former jurisdictions was decided by drawing lots 12.