The book of Exodus took place in 1446 BC. Although archaeology shows no mass destruction until the 1200s and there is no written recorded other than the Bible describing 2 million salves leaving Egypt, the Bible shows more evidence of this date. In Kings and Judges it describes Kings, people, and circumstances that were closer to 1446 rather than 1260.
The times and dates in the Bible are taken very seriously and literally. I believe that if everything is to be taken seriously in the Bible, such as turning the Nile into blood and flooding the entire earth, then we must take everything including dates seriously.
Arnold, Bill T., and Bryan Beyer. Encountering the Old Testament: A Christian Survey. Grand Rapids, MI: Baker, 1999. Print.
Robinson, Thomas L. The Bible Timeline. Nashville: T. Nelson, 1992. Print.