[Note: Assuming a twenty-year period of time in Harran creates a problem in the chronology of the births of Judah’s children, making some to be as young as eight and nine years old when they were married.]
[Note: By a simple chronological method we can figure that Jacob lived for more than 20 years in Harran. We can do this by using a confirmed date for the birth of Abraham, or we can simply use Abraham as a reference point to examine the chronology of his family.
We know that Isaac was born when Abraham was 100 years old, and we also know that Jacob was born when Isaac was 60 years old. Then Isaac died 120 years after Jacob was born, and Jacob died in Egypt at the age of 147.
Now when Joseph was 17 years old he was sold into slavery by some of his brothers, and he was in Egypt for 13 years when he became Prime Minister at the age of 30. Then we know that there were seven years of plenty in the land, followed by seven years of famine, and it was after two years of famine that Jacob went into Egypt with his family, when Joseph was 39 years old. We also know that Jacob was 130 years old when he went into Egypt (Gen. 47:9).
This allows us to conclude that Jacob was 130 years old when Joseph was 39 years old.
Then by simply counting backward on the scale of time we see that Jacob was 91 years old when Joseph was born in Harran, and the six years of working for the livestock ended when Jacob was 97 years old, and he was 98 in his first year back in Canaan. So we see that Joseph was a child of Jacob’s old age (Benjamin also).
However if we assume then that Jacob was only 20 years in Harran, then he would have been 77 years old when he went to Harran and 78 years old in his first year in Harran. Consequently by a twenty-year reckoning Jacob would have been 85 years old when he married Leah and Rachel.
This is not probable.
But let’s look at another chronology respective to Jacob’s brother Esau.
Esau went to Ishmael to marry one of Ishmael’s daughters while Jacob was on his journey to Harran. Ishmael was a son of Abraham and half-brother to Isaac, and he was also 14 years older than Isaac. That means Jacob and Esau were born when Ishmael was 74 years old, and Ishmael died when he was 137 years old, which was 67 years before Isaac died (Gen. 28:6-10).
By calculating from the death of Ishmael to the births of Jacob and Esau, we find that they were only 63 years old when Ishmael died. That tells us that the oldest Jacob could have been was 63 years old when he left for Harran, if he left about the time Ishmael died. That alone is reason enough to confirm a period of no less than 34 years chronologically for Jacob’s time in Harran, and therefore we can conclusively rule out a twenty-year period in Harran.
However, because Ishmael was still alive when Jacob left Canaan, then Jacob was some years younger than 63 years old when he left for Harran.
Finally, if we take Jacob’s stated account to be true, we know that he worked 40 years for Laban, which means he was 57 years old when he left Canaan, and he was age 58 in his first year in Harran, and he married Leah and Rachel when he was age 65, and at age 97 he completed his 40 years living with and working for Laban, and finally at age 98 he returned to his father’s house in Canaan.] 
(How Long Did Jacob Wrestle with Laban?–Part Two)
