The blog Tough Questions Answered has a good five-part series addressing the question “What is the meaning of the word ‘day’ in Genesis?” The posts take a look at reasons why the six days of Genesis 1 are not necessarily six literal consecutive 24-hours days.
Young-Earth creationists have much of the Evangelical world convinced that the Bible requires a young Earth, and that to allow for an old Earth is a compromise of some sort. In reality, it is often the old-Earth Christians who have taken the closest look at what the text actually says and how this fits into the cultural setting of second century BC Israel. There are many instances where it is the young-Earth creationists who are reading more into the text than what it actually says.
Grace and Peace