It is an auspicious day in Islam. The day celebrates the start of a new year in the Islamic calendar. The day occurs annually on the first day of the month of Muharram in the Islamic calendar. The day was chosen to mark the holy journey that the Prophet Muhammed took from Mecca to Medina and is celebrated by Muslims all over the world. It usually does not occur on the same date every year, as the Islamic calendar is based on lunar cycles.