Complex sentence: The Mourning of Muharram, Remembrance of Muharram, or Muharram Observances, is a set of rituals associated with both Shia and Sunni, which takes place in Muharram, the first month of the Islamic calendar.
Split into simpler sentences: The Mourning of Muharram (or Remembrance of Muharram or Muharram Observances) is a set of rituals associated with both Shia and Sunni Islam. The commemoration falls in Muharram, the first month of the Islamic calendar.