Genesis 8:13

"And it came to pass in the six hundred and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering from the ark, and looked, and, behold, the face of the ground was dried."

The exit from the ark took place one month and 27 days later than the time specified here, as revealed in Genesis 8:14; and presumably, Noah might have taken it upon himself to leave the ark during that period, but he patiently waited until God gave him the signal to disembark. After all, God had told him to enter and had closed the door, and Noah evidently decided to wait until God opened the door or commanded him to leave.