Regarding the time for Hajj, Allah says: (The pilgrimage is (in) the well-known months, and whoever is minded to perform the pilgrimage therein (let him remember that) there is (to be) neither lewdness nor abuse nor angry conversation in the pilgrimage) (Al-Baqarah 2:197).
This verse refers to the season of Hajj, as the days of Hajj rituals starts with the Dhul-Hijjah 8, and it ends with the 3rd day of Tashreeq (Dhul-Hijjah 14).
On this issue, Dr. Salah Sultan, stated that
‘The verse means that the Hajj season starts from Shawwal till Dhul-Hijjah for those who want to do Tamattu` or Qiran type of Hajj.
If one makes `Umrah on Shawwal and then on Dhul-Hijjah 8 starts the Hajj, then he or she has done Tamattu` Hajj for which slaughtering sacrifice is needed.
If the pilgrim has started on the 5th or 6th of Dhul-Hijjah, then he or she has done Qiran Hajj for which slaughtering sacrifice is also needed.
Almighty Allah says, (If one [the pilgrim] wishes to continue the `Umrah on to the Hajj, he [or she] must make an offering such as he [or she] can afford) (Al-Baqarah 2:196).