The pilgrimage must take place during the month of Dhu al Hijja, the last month of the Islamic calendar. The rites of Hajj are performed from the 8th to the 12th of Dhu al Hijjah.
As the Islamic calendar is based on the lunar year, the date changes in the Gregorian calendar each year, and is 10 to 11 days earlier than the preceding year. In 2017, it is expected to be on or around August 30th or September 1st.