Adam Clarke on Genesis 34:1

And Dinah - went out to see the daughters of the land - It is supposed that Jacob had been now about seven or eight years in the land, and that Dinah, who was about seven years of age when Jacob came to Canaan, was now about fourteen or fifteen. Why or on what occasion she went out we know not, but the reason given by Josephus is very probable, viz., that it was on one of their festivals.