Presidential Decree No. 1083 recognized Eid al-Fitr as a legal Muslim holiday for Muslim Filipinos.
Issued in 1977 under President Ferdinand Marcos, the decree established the Code of Muslim Personal Laws of the Philippines. Its provisions recognized several official Muslim holidays, including Id-ul-Fitr, also called Hari Raya Pausa, on the first day of Shawwal, the lunar month following Ramadan.
The decree specified provinces and cities where Muslim holidays were officially observed, including areas in Mindanao and the Sulu Archipelago. It also provided that Muslim government officials and employees elsewhere could be excused from work to observe Muslim holidays. Dates were to be determined according to the Muslim lunar calendar.
This historical provision should be distinguished from later nationwide holiday legislation. Republic Act No. 9177, passed in 2002, declared the first day of Shawwal a regular holiday throughout the Philippines, subject to the date being set through the Islamic calendar. Thus, “Muslim Filipinos” is the canonical group in the question, not Catholic Filipinos, teachers, or overseas workers.