8 Days
Thus, He completed them as seven heavens in two days, assigning to each its function. And We adorned the lowest heaven with lamps and protection. Such is the decree of the Almighty.
41:12Then He ordained them seven heavens in two Days and inspired in each heaven its mandate; and We decked the nether heaven with lamps, and rendered it inviolable. That is the measuring of the Mighty, the Knower.