I have heard over the course of my years a number of preachers and individuals talk about the 430 years that the Israelites were in slavery in Egypt.  There are two things that make this an incorrect assertion.

1. Galatians 3:16-17 - 16Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.17And this I say, that the covenant, that was confirmed before of God in Christ, the law(*1), which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.

Paul is writing about the promise to Abraham concerning Christ.  He then says the covenant (the promise to Abraham) that was confirmed in Christ could not be disannulled and made of no effect by the law (the Law of Moses) which came 430 years after.  Paul quite plainly says that the law (of Moses) came 430 years after the promise to Abraham.  This is quite simply a contradiction to the idea that the Israelites were in Egypt for over 4 centuries.  The pure histories (which are based on this false assertion to a degree also) get it wrong.

*1 As a side note, it is important once again to point out that Paul here refers to the Law of Moses simply as "the law" unmodified.  He does this in every letter he wrote.  It is a given in his letters that when we see the term "the law" he is speaking about the Law of Moses.  Only when Paul modifies the phrase "the law" by something that we may understand it to be something else.

2.  A more subtle approach to understanding why the Israelites could not have been in Egypt for 430 years is the lineage of Moses.  From Genesis 46 (vs. 11 specifically) we learn that Jacob, with his entire family,  moves to Egypt under Joseph's reign as Pharaoh's second.  His son Levi has already had his own children, among whom is Kohath.  In Exodus 6:18 we know that Kohath bears a son named Amram while in Egypt.  Amram grows up and marries a woman of Levi named Jacobeth, who is his aunt (*2), Kohath's sister (Ex. 6:20).  Amram and Jacobeth bear Aaron and Moses.

Now, Kohath only lived 133 years and part of those years were before Egypt and part of those years were after he bore Amram.  Amram lived to be 137 and part of those years were after he bore his younger son, Moses.  Moses grew up in Egypt and fled when he was 40.  He spent 40 years in the wilderness making him 80 when the Israelites left Egypt (and then another 40 in the wilderness, where he died just before they entered the promised land).

At most with these numbers we are looking at 350 years if you add up all the numbers.  Since we know that is not the case, it is closer to 200 something years that the Israelites were in Egypt.  Only three generations of Levites were in Egypt, considering their longer life spans.  450 years is waaaay too long a time and an incorrect statement to make. 

Please check your facts before stating things like this from a position of authority.

*2  Remember that it was not until during the 40 years of wandering, well after Moses was born to Jacobeth and Amram, that incest was condemned in scripture (which has to do with the flood, the loss of the 'waters above the heaven', and the genetic degradation caused by the bombardment of UV radiation).  Leviticus 18 was more than 80 years after the marriage of Amram to his aunt and not sinful.

In Truth and Love