The Islamic calendar, also known as the Muslim or Hijiri calendar, is the only widespread calendar used today that is a true lunar calendar. This means it is a calendar based off of 12 lunar months with 354 or 255 days in a year. It is used by Muslims all around the world to determine the Islamic days of holiness and other traditional Islamic festivals. The first year on the Islamic calendar was the year in which the profhet Muhammad emigrated from Mecca to Medina, known as the Hijira. Currently, the Islamic calendar is on year 1431.

The twelve lunar months of the Islamic calendar are Muharram, Safar, Rabi’al-awwal, Rabi’ al-thani, Jumada al-Ula, Jumada al-Thani, Rjab, Sha’aban, Ramadan, Shawwal, Dhua al-Qui’dah, and Dua al-Hijjah. Of these twelve months, Ramadan is the most recognized and is a time in which Muslims go without eating, drinking, and sexual activity during the daylight of each day of the month.

The Islamic lunar calendar used to have great significance to the daily life of most Muslims. The significance of the lunar calendar has decreased in present day. Today, the Islamic calendar is used soley for religious reasons by determining the correct religious celebratory dates and public events in Muslim countries. Since it is a pure lunar calendar, it cannot be used in daily life in agriculture or government purposes.. Historically, Muslim communities have used alternative calendars for these purposes.