The first difficulty in determining the timeline is whether the births recorded in Gen 29-30 occurred in the order recorded. There is nothing in the text that indicates that the precise order of naming in the text was the order of birth. The text more clearly establishes, however, that Reuben was the firstborn, while Dinah and Joseph were born last.
Even so, even if Leah had one child per year, Reuben could be no less than seven years older than Dinah; perhaps he was considerably older, because “Leah saw that she had left bearing” (Gen 30:9) for a time, implying that there was a gap, probably of some years, between Judah and Issachar. Now, Leah began her childbearing, presumably, in the eighth year of Jacob’s sojourn in Haran, meaning that the earliest that Dinah could have been born was around the 16th year of Jacob’s sojourn. Therefore, Dinah was likely not older than four years old when the family left Haran.
Now, Jewish scholars reading the Mishnah said a girl could be betrothed—and a marriage consummated—as early as three years old. The idea is incredibly repugnant, of course, and most commentators assume Dinah was a teenager, although this is only a conjecture. To tip my hand here: we really have no idea how old she was, but there are good reasons for the conjecture "she was a teenager."
She went visiting by herself, something certainly no little girl would do, nor would be allowed to do; but perhaps, you might say, she was with other, older females? Perhaps. If she were (incredibly) a very little girl, surely the text would note that fact.
So let us assume that considerable time has passed, i.e., it was not mere weeks or months between the events of Gen 33 and Gen 34, but years. Where would the family have passed the time? One possibility is that the family spent significant years at Succoth, as perhaps implied by the fact that they built a “house” there (33:17).
Another possibility is that they spent years in the family property outside of Shechem, as perhaps implied by the facts that they purchased land, and that the suggestion that the tribes be intermixed was treated seriously on both sides.
A final possibility is that, though we are not told so, Jacob resumed his father’s and grandfather’s nomadic ways, and Shechem was merely one of their stopping-places; a reading of Gen 35 does not rule this out, but makes it somewhat less likely.
Finally, and perhaps most importantly, we should also take stock of the fact that at least some brothers are called “men.” Assuming manhood began at age 20 (when a boy’s value increases from 20 to 50 shekels: Lev 20:3), and assuming Simeon and Levi were born 9 and 10 years into Jacob’s Haran sojourn, it follows that these boys were 11 and 10 when Jacob met Esau, and so another 10 years, at least, had to have passed.
This should not be too surprising since gaps in the narrative are often passed over in total silence in the Bible. So it is entirely possible that Dinah was in her teen years, with her oldest brothers in their 20s.
