Reconciling the 430 yrs mentioned in Galatians and the 400 in Genesis 15:13?

Full Question

Answer

In Genesis 15:13 God tells Abraham that his descendants will be sojourners in a land that is not theirs. Obviously this “sojourning” of Abraham’s seed could not begin until he had a seed, and Isaac was not born until Abraham was 100 years old. Abraham was 75 years old when he left Haran, but this was some considerable time after they left Ur, where the promise was given. This period involved the time preparing for leaving Ur, their journey to Haran, and the closing years of Terah’s life, and it completes the difference between the 25 years and the 30 years. Abram must therefore have been 70 years old when God made the first promise to him.

The oppression, however, was nothing like 400 years in duration, neither is it necessary to make Genesis 15:13 say so. It is obvious that a parenthesis is involved, and the statement should read, “… know of a surety that your descendants will be sojourners in a land that is not theirs (and will be slaves there and they will be oppressed) for four hundred years …”.

The question then arises, how long were they oppressed? Note the following :

Birth of Isaac to birth of Jacob	60 years
Birth of Jacob to his standing before Pharaoh (when Joseph was 30 ± 7 ± 2 years old)	130 years
To end of Joseph’s life (110 years old when he died)	71 years
To birth of Moses	59 years
To Exodus	80 years
Total	400 years

We know the oppression had begun when Moses was born, but we do not know how long it was after Joseph died before it began. It does mean, however, that the oppression must have been something less than 139 years, but conjecture cannot get us any further. We are simply told “Another king arose who knew not Joseph”, and presumably this took place when the Hyksos dynasty was overthrown and native Egyptians once more ruled the land.

It is interesting to note that Exodus 12:40 says that it was “on the very day” of the conclusion of the 430 years that Israel marched out of Egypt. It is also obvious that in this verse the phrase “who dwelt in Egypt” is in parenthesis. We think it is also evident that the phrase “the Children of Israel” includes the days of Abraham after the giving of the first promise in the land of Ur, otherwise both Isaac and Jacob would have to be excluded, seeing they were not “children of Israel” but rather their ancestors.