Islamic holidays
There are two official holidays in Islam, Eid al-Fitr in addition to Eid al-Adha. Both holidays arise on dates in the lunar Islamic calendar, which is different from the solar-based Gregorian calendar, so they are observed on different Gregorian dates every year. There are a number of other days of note in addition to festivals, some common to any Muslims, others particular to Shia Islam as a whole or branches thereof.
Both Eid al-Fitr and Eid al-Adha follow a period of 10 holy days or nights: the last 10 nights of Ramadan Eid al-Fitr, and the number one 10 days of Dhu al-Hijjah Eid al-Adha. The Night of Power, one of the last 10 nights of Ramadan, is the holiest night of the year. Conversely, the Day of Arafah, the day ago Eid al-Adha, is the holiest day of the Islamic year.
Additionally, Friday is considered the holiest day of the week, and in Islamic tradition, is considered a celebration in itself. Friday Prayers Juma are congregational prayers held in mosques, and Muslims are encouraged to wear clean and refined clothes, perfume, and bathe. It's customary to eat special meals with family on this day.