What it marks
National Day celebrates the unification of the Kingdom, proclaimed by King Abdulaziz bin Abdulrahman Al Saud. By a royal order dated 17 Jumada al-Ula 1351 AH, the name of the state changed from the Kingdom of Hejaz and Najd and its Dependencies to the Kingdom of Saudi Arabia.
The order chose the first day of the month of Libra, which fell on Thursday 23 September 1932, as the day to declare the unification.
A day for the whole country
According to Saudipedia, a royal decree under King Faisal bin Abdulaziz established it as a national day in 1965, and it became an official public holiday in 2004. It is celebrated every year on 23 September.