Muharram is the first month of the Islamic, or Hijri, calendar, and one of four sacred months during which Islam forbids warfare and encourages increased prayer, charity and reflection. The most important day is called Ashoura, which commemorates the martyrdom of the grandson of the Prophet Muhammad, Hussein, who was killed in 680 battle in present-day Iraq. While the passage of the Islamic new year is generally more solemn and introspective than festive, Muslims may observe the holiday differently, according to their school of thought.