"In the beginning, God created the heavens and the earth." (Gen 1:1) On that all agree whether we hold to Evolutionary Creation, Intelligent Design, Young Earth Creationism or the Gap Theory. We all take that literally. Why not, the Young Earth Creationists say, do we not take the rest of that chapter, and all subsequent chapters, literally? The Evolutionary Creationists and the Intelligent Design advocates do not take the "six days of creation" as literal 24-hour time periods. Rather they say that these "days" represent long ages of time. And, of course, the word "day" does sometimes mean a time period other than a 24 hour period. The Day of the Lord, for example, lasts more than a thousand years.
But we have to read this in context. It talks about evening and morning, and it speaks of multiple days. That is quite different from speaking about "the Day of the Lord." Nobody using the word 'day' talks about evenings and mornings. Those are spoken of only in the context of literal days.
Young Earth Creationists take all of Genesis literally as possible stating that the earth is no more than 6000 to 10,000 years old. Perhaps you have heard of Bishop Ussher's calculations and telling us that the creation occurred in 4004 B.C. He got that number by adding up all the genealogies and the ages of the men who begot a son who begot a son and on and on. This is the natural way for us to read these genealogies. And it is not really the proper way to read them. Generations were skipped in ancient genealogies even if the author knew who belonged there.
I have included a quote here of the issue of skipped generations in biblical genealogies. It is from http://www.trustbible.com/genealogies.htm if you wish to read the whole article. It is a concise summary of the matter.
"A close study of the Biblical text shows us there were gaps in the Biblical genealogies. I believe the original writers and readers of the Bible understood and knew the genealogies were correct but incomplete ... Matthew 1:8 tells us that Joram fathered Uzziah. However, in 1st Chronicles 3:11-12 we find that Joram fathered Ahaziah, who fathered Joash, who fathered Amaziah, who begot Uzziah who was also called Azariah. To see that Uzziah was also called Azariah compare 2nd Kings 14:21-22 with 2nd Chronicles 26:1-2."
The terms 'father' and 'son' have a much broader meaning in the Bible than they do today. A 'father' could be a great, great ... great grandfather - without limitations. So, simply adding up the years in the genealogies will not work. In the light of these facts, we need to read the genealogies as ancient people would read them.
Seth lived one hundred and five years, and became the father of Enosh ... Enosh lived ninety years, and became the father of Kenan ... Kenan lived seventy years, and became the father of Mahalalel ... Mahalalel lived sixty-five years, and became the father of Jared. (Genesis 5:6-15)
The "natural" reading of this passage puts 390 years between Seth and Jared. But what about generations that were skipped. If we assume those (and that is a very good assumption given the biblical record as a whole), we must read it differently. So when Seth was 105 years old, he fathered a child whose ancestor would be Enosh and when Enosh was 90 years old he fathered a child whose ancestor was Kenan. If we read it this way, and it is a justified way to read it without distorting the text, we cannot say that there were only 390 years between Seth and Jared. There could have been many, many more years.
Why skip generations? Well, first we would have an even longer Bible than we have now. In fact, in light of what we have learned about genealogies I think most Christians would shorten them even further so that there is not all that stuff to read! It seems that Genesis only records the most prominent ancestors of one person or another. Most have heard of Winston Churchill, the famous British Prime Minister who saved England in WW2. He had an ancestor, the Duke of Marlborough, who was famous in holding off the French Forces of Louis XIV in the seventeenth century. In our history books, both men will be mentioned but likely none of the men in the generations that separated them. They are not relevant.
Some Creations Scientists do insist on the 6000 years, but many read the genealogies as I have suggested and they will say that the number is more like 10,000 years. I even know of one scholar who suggests that it ought to be more like 35,000 years though I cannot recall why he prefers this figure. But I have no problem with any of these figures because it still fits within a literal reading of Genesis. We have not departed from that.
The interpretive issue here is not "literal vs. nonliteral" interpretation, but "ancient vs. modern". Most modern Christians do not really understand how ancient genealogies worked. We thought we were "just taking the Bible for what it says" but were really ignorant of how it was read in ancient times. Most of the time that we read we can just take the plain meaning of the scripture and it will be right. But there are times when there is a cultural distance between ourselves and those who wrote the Bible. That is when we need scholars to help us understand better. Some things we are so certain about can turn out to be quite wrong.
In conclusion, I must say that I agree more with the Young Earth Creationists who think that the Bible allows us to think that the earth is more than 6000 years old than with those who read the genealogies in a rigid manner requiring those who take Genesis literally to hold to 4004 BC as the date of the creation. Our ancient forebears did not hold to the strict standard of some Young Earth Creationists.