As in most Middle Eastern countries, the weekend in Saudi Arabia is Friday and Saturday, with Sunday being a normal working day. (Until 2013, it was Thursday and Friday).
The Saudi interpretation of Islam tends to regard non-Muslim holidays as blasphemous, and the public observance of Christmas, New Year, Valentine’s Day, Halloween, etc. is forbidden. Public holidays are only granted for Eid ul-Fitr, the festival at the end of the fasting month of Ramadan, Eid al-Adha, commemorating Abraham’s willingness to sacrifice his son, about 70 days after Ramadan.
There is also a secular holiday: Kingdom Unification Day, on 23 September. Strictly speaking, it is not a holiday or a festival, although it is treated as one nonetheless. In fact, it is celebrated more eagerly by many local youth than the Islamic Eid.
During Ramadan itself, visitors must abide by the restrictions of the fasting month, at least in public: no eating, drinking or smoking during daylight hours. Some better hotels will be able to provide quiet room service during the day, but otherwise you will need to make your arrangements. All restaurants in the Kingdom are closed during the day, and while some offices remain open with limited hours, the pace of business slows to a standstill. After evening prayers, however, all restaurants in the bazaar open and do a brisk trade until the early hours of the morning. Most of the shops are also open, and the coolness of the evening makes it a pleasant time to shop. A visitor can have a good time on these evenings, although for most visitors it is better to have a stash in the hotel room for a quiet breakfast around ten o’clock than to get up at four to enjoy a big Saudi breakfast before dawn.