The Simplest Scriptural Case for a Young Earth

Exodus 20:8-11

⁸ “Remember the Sabbath day, to keep it holy. ⁹ Six days you shall labor and do all your work, ¹⁰ but the seventh day is the Sabbath of the Lord your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who is within your gates. ¹¹ For in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the Lord blessed the Sabbath day and hallowed it.

This is one of two prooftexts I would use to prove that the days of Genesis 1 are 24-hour days. Here it clearly states that the length of the days that God created are the same length of the days of our week. 

"That's why," said Ken Ham in this video of a speech he gave entitled The Key to Reclaiming the Culture, "we have a seven-million-year week."

Said as obvious sarcasm. Since our week is not millions of years long, but seven times 24 hours, then that is how long Creation Week also was. To believe otherwise is to assert that Exodus 20 -- you know, the part where Moses gets the 10 Commandments -- is not inspired Scripture, and can't be relied upon to be true.

Beliefs have consequences, you know.

That's really the only prooftext you need. But there is another one that I find poignant as well:

Genesis 1:14
¹⁴ Then God said, “Let there be lights in the firmament of the heavens to divide the day from the night; and let them be for signs and seasons, and for days and years; 

If "day" means "billions of years," or rather "an undefined long period of time," then what on earth do "seasons" and "years" mean? These are longer than days. Are we supposed to postulate that there are two types of 'undefined long periods of time,' one which is longer than the other, but neither one of a certain duration? This is silliness.

Consequently, verse 14 proves that the days in the rest of the passage must refer to calendar days, since otherwise it would be a meaningless passage.

These passages should be enough to convince anyone who holds to Biblical inerrancy. If they reject the conclusion that Genesis 1 is describing a one-week period of time of the same length that our week is, Sunday to Sunday, then they must abandon their belief in Biblical inerrancy. It's always interesting to see which way people go when confronted with such a decision. It is my hope that they would be more willing to change their mind to believe God's word than to reinterpret God's word to make it fit with man's word.

Perhaps this has convinced you, Scripturally, but you're uncertain/worried about the scientific arguments--whether what the Bible says is borne out by the facts. Do not worry. I assure you that they do. Here are a few good links to get started investigating the issue further, if you want to.

http://www.answersingenesis.org/get-answers/topics-alphabetical
http://creation.com/age-of-the-earth

~ Rak Chazak