Much of the world today follows the Gregorian solar calendar, which has its origins in medieval Western Christianity. Conversely, the Islamic calendar or Hijrī, is a lunar calendar. There are 12 months in the Hijrī calendar, with each month being 29 or 30 days long.
It would be over 32 to 33 years that the lunar calendar will completely cycle the solar calendar. That's why the Islamic fasting month of Ramadan can fall in October one year, and a few years later it would be in July. It also means that the Islamic New Year is never on the same date and would also depend on the sighting of the moon.
Year one of the Hijrī calendar is based on the emigration of the Prophet Muhammad from Mecca to Medina in the year A.D. 622 to establish the first Muslim community. Despite Muhammad being from Mecca, his new faith and followers were persecuted for their beliefs. The Islamic calendar marks that beginning in Medina.
Additionally, the Islamic New Year is associated with the prophets of the Christian faith as well: This is the day when Noah's ark is believed to have come to rest on land, the day on which God forgave Adam, the day of Joseph's release from prison, the day of the births of Jesus, Abraham and Adam, throughout the ages. It is also believed to be the day of the Prophet Muḥammad's conception in the year 570.
Currently, while much of the world sees this as 2021, it is the Islamic year 1443, starting on Aug. 10 A.H. In Latin, A.H. means Anno Hegirae – the year of the hijra, or emigration.
Unlike many traditions that celebrate the new year as a joyous occasion, the Islamic New Year is typically a somber affair. The first Islamic month is Muḥarram, a sacred time for prayer and reflection for both Sunni and Shiite Muslims.