Exact correct time to begin and end the I’tikaf?

Answer By Dr Zakir Naik,As far as beginning of Ietikaaf for the last ten days of Ramadhaan is concerned there is a difference of opinion between the scholars. One group of scholars… people like Al Awza’ee, people like At Thawari, or Imaam Al Layth (may Allah be pleased with them all), they says that Ietikaaf should begin after the Fajr Salaah, on the 21st night, based on the Hadith which is mentioned in
Sahih Bukhari, Vol. No. 3, in the Book of Ietikaaf, Hadith No. 2034 as well as 2041, that Hadhrat Ayesha (may Allah be pleased with her) she said that,
“The Prophet used to do Ietikaaf for the last ten days of Ramadhaan and I used to pitch the tent for him. And after Fajr Salaah he used to come at the place of Ietikaaf and enter the tent.”