KUALA LUMPUR: The date of Hari Raya Aidilfitri in Malaysia will be decided based on Hisab (astronomical calculations) and Rukyah or the sighting of the new crescent moon (hilal) as soon as the sun sets on the 29th day of Ramadan, which is on Thursday (April 20), says Federal Territories (FT) Mufti Datuk Dr Luqman Abdullah.