The short answer
Morocco has fixed holidays on the same date each year, including 1 January, 11 January, Yennayer in mid-January, 1 May, 30 July (Throne Day), 14, 20 and 21 August, 6 November and 18 November. On top come the Islamic holidays, which move with the moon: the two Eids, Islamic New Year and the Prophet's Birthday.
In more detail
The fixed dates are New Year's Day (1 January), Independence Manifesto Day (11 January), Yennayer, the Amazigh New Year (13 or 14 January; check the day), Labour Day (1 May), Throne Day (30 July), Oued Ed-Dahab Day (14 August), Revolution of the King and the People (20 August), Youth Day (21 August), Green March Day (6 November) and Independence Day (18 November).
The Islamic holidays move about eleven days earlier each year. In 2027, Eid al-Fitr is expected about 9 to 10 March and Eid al-Adha about 16 to 17 May. These are the ones that change a trip: many shops and local restaurants close, and transport is packed.
On fixed holidays, banks, government offices and some shops close, but riads, restaurants and the main sights mostly carry on. Throne Day brings flags and lights to the city. In 2027, 1 January falls on a Friday, so it is both a holiday and the day of the main weekly prayer.