Constitution Day (Hari Konstitusi Republik Indonesia) is observed in Indonesia every August 18 to commemorate the ratification of the 1945 State Constitution. Established by a presidential decree in 2008, this day highlights the historical significance of the constitution, which was drafted during the final months of Japanese occupation. The foundation for the constitution was laid by the Investigating Committee for Preparatory Work for Independence (BPUPK), led by Rajiman Wediodiningrat, with notable members including Sukarno and Mohammad Hatta. The Committee of Nine, which included a diverse group of nationalists, presented the Jakarta Charter that influenced the constitution's preamble. Following Japan's surrender, the constitution was officially adopted on August 18, 1945. Although not a public holiday, Constitution Day is celebrated the day after Indonesia's Independence Day, emphasizing the importance of the constitution in the nation’s history.