His Majesty’s Accession Day is observed in the United Kingdom on September 8, commemorating King Charles III’s accession to the throne in 2022. This day is one of the designated flag-flying days when the Union Flag is flown on all government buildings. The tradition of marking Accession Day began with Queen Elizabeth I, whose accession was celebrated with processions and festivities. The current form of the celebration originated in the 20th century, with notable observances including a Royal Gun Salute in London and special church services across the Church of England. While churches of other denominations may choose to hold services, it is not a requirement. It is important to distinguish Accession Day from Coronation Day, as the former occurs immediately upon the death or abdication of a monarch, while the coronation ceremony takes place later.