Death

One of the arguments for a young earth is the death argument i.e. before the fall there was no death for all life including the animals. This is usually based on the Rom 5:12-14 passage cited below:

(Rom 5:12-14 NIV) Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all men, because all sinned-- {13} for before the law was given, sin was in the world. But sin is not taken into account when there is no law. {14} Nevertheless, death reigned from the time of Adam to the time of Moses, even over those who did not sin by breaking a command, as did Adam, who was a pattern of the one to come.

However if we look at the actual passage in Genesis, eternal life was contingent upon Adam eating from the fruit of the tree of life. He was barred from this and hence physically died (eventually) see Gen 3:22-24. There is no evidence that eternal life was available for animal life. The passage in Romans refers to the death of Adam and mankind not to the animals.

(Gen 3:22-24 NIV) And the LORD God said, "The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever." {23} So the LORD God banished him from the Garden of Eden to work the ground from which he had been taken. {24} After he drove the man out, he placed on the east side of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life.

In Rev 22:1-2 we find again the tree of life which is again freely available to those who overcome and those who wash their robes, see Rev 2;7 and 22:14.

(Rev 22:1-2 NIV) Then the angel showed me the river of the water of life, as clear as crystal, flowing from the throne of God and of the Lamb {2} down the middle of the great street of the city. On each side of the river stood the tree of life, bearing twelve crops of fruit, yielding its fruit every month. And the leaves of the tree are for the healing of the nations.

(Rev 2:7 NIV) He who has an ear, let him hear what the Spirit says to the churches. To him who overcomes, I will give the right to eat from the tree of life, which is in the paradise of God.

Rev 22:14 "Blessed are those who wash their robes, that they may have the right to the tree of life and may go through the gates into the city.

The death of plant life before the fall is implied by the fact that every green plant was given to the animals for food Gen 1:30.

(Gen 1:29-30 NIV) Then God said, "I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. {30} And to all the beasts of the earth and all the birds of the air and all the creatures that move on the ground--everything that has the breath of life in it--I give every green plant for food." And it was so.

See Death Before the Fall by Glenn R. Morton and Does the Bible Teach a Young Earth? By Matt Perman, In Adam All Die?

The Seventh day

An argument in favour of a young earth is the literal translation of the six days of creation which all end in the phrase - And there was evening, and there was morning--the xth day. But in the case of the seventh day this formula is not repeated, see Gen 2:1-3.

(Gen 2:1-3 NIV) Thus the heavens and the earth were completed in all their vast array. {2} By the seventh day God had finished the work he had been doing; so on the seventh day he rested from all his work. {3} And God blessed the seventh day and made it holy, because on it he rested from all the work of creating that he had done.

This seventh day is also mentioned in Hebrews 4:4.

(Heb 4:1-10 NIV) Therefore, since the promise of entering his rest still stands, let us be careful that none of you be found to have fallen short of it. {2} For we also have had the gospel preached to us, just as they did; but the message they heard was of no value to them, because those who heard did not combine it with faith. {3} Now we who have believed enter that rest, just as God has said, "So I declared on oath in my anger, 'They shall never enter my rest.'" And yet his work has been finished since the creation of the world. {4} For somewhere he has spoken about the seventh day in these words: "And on the seventh day God rested from all his work." {5} And again in the passage above he says, "They shall never enter my rest." {6} It still remains that some will enter that rest, and those who formerly had the gospel preached to them did not go in, because of their disobedience. {7} Therefore God again set a certain day, calling it Today, when a long time later he spoke through David, as was said before: "Today, if you hear his voice, do not harden your hearts." {8} For if Joshua had given them rest, God would not have spoken later about another day. {9} There remains, then, a Sabbath-rest for the people of God; {10} for anyone who enters God's rest also rests from his own work, just as God did from his.

From this I would conclude that we are still in the seventh day.

With regard to the length of the seventh day Matt Perman makes the following comment: "On the sixth day of creation (1) God created the higher forms of animals, (2) God created Adam, (3) God planted a garden in Eden, (4) God made to grow the vegetation in Eden, (5) God gave Adam the responsibility for tending the garden, (6) Adam became lonely, (7) God had Adam name all of the animals, in search of a companion, (8) Adam was still lonely after this, (9) God put Adam into a deep sleep and made Eve from his rib, (10) Eve was presented to Adam as his new partner, and finally (11) God gave them instructions to multiply and care for the earth. (See Genesis 1:24-30; 2:4-24). How could all of these events have been completed in only twenty-four hours? At the very least, they would have taken several months."

See Does the Bible Teach a Young Earth? By Matt Perman