"They are right"... hmmm pretty bold. By what authority do you make this claim? I will believe the word of God before any speculation of man.
If we apply oakum's razor to this issue... as a default. The simplest explanation and the one written in God's word will be considered the truth.
God said He did it in six days, He is capable of doing it in six days.... It was done is six days. Any erroneous data gathered and interpreted by man is second place.
The issue here is twofold: first, creation of life is a separate issue from the creation of the universe, and second, the Bible simply does not indicate how old the Earth is.
A close reading of Gen 1 keeps open the possibility of an old earth (Gen 1:1-8 is all we really need):
Gen 1:1 In the beginning, God created the heavens and the earth.
Gen 1:2 The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters.
Gen 1:3 And God said, "Let there be light," and there was light.
Gen 1:4 And God saw that the light was good. And God separated the light from the darkness.
Gen 1:5 God called the light Day, and the darkness he called Night. And there was evening and there was morning, the first day.
Gen 1:6 And God said, "Let there be an expanse in the midst of the waters, and let it separate the waters from the waters."
Gen 1:7 And God made the expanse and separated the waters that were under the expanse from the waters that were above the expanse. And it was so.
Gen 1:8 And God called the expanse Heaven. And there was evening and there was morning, the second day. (ESV)
Notice in verse 1 that "God created the heavens and the earth." Then verse 3 begins with "And God said." God does some things and then the first day ends in verse 5 with "And there was evening and there was morning, the first day." Verse 6 then begins with "And God said." God does some more things and we see in verse 8 "And there was evening and there was morning, the second day."
And so we see for days two to five that they begin with "And God said." But verse one doesn't start that way and yet it says "God created the heavens and the earth." It would seem then that day one doesn't then begin until verse 3, "And God said." This leaves open the possibility that the earth could be very old.
Those who are so adamant that the Earth is young are presuming too much. The text is silent on the age of the Earth. And this does not mean that God didn't create the rest in seven 24-hour days. There are numerous ways of looking at the text, so to just simply say that one believes the Bible as though someone who believes differently does not, is really to be basing that statement on certain presumptions which may or may not be true. We have to be much more careful than that.