Time itself was created at the beginning of the universe, and time itself, as well as space expanded into the very large space time that we inhabit.
This means a period of time equivalent to 6 terrestrial days (as is implied by Moses) may in fact appear to be a lot longer time from an observation point within the created universe.
This is one inference from General Relativity and has been expermientally verified. The Rabbi Maimonides, in the 12th century determined this from the first verses of Genesis and of course the work of Albert Einstein brought the idea into popular scientific thought.
This article is informative:
http://www.aish.com/ci/sam/48951136.html
So given the difference in perspective that relativity yeilds, who would be lying about how long things took to the person who claimed 6 days or the person who claimed a much longer time frame from their observation point? The answer is that neither is lying.
We can take the word of God literally because He is the Creator and the one who is telling the story from His perspective but we can also understand that time and space itself unfolded as it was created to make a space and time big enough for Gods creation to dwell within.
This is understanding and means that while we can confirm in our own minds that the observations of an apparantly old universe and earth are valid, we don't need head down some slippery slope of maligning the integrity of God.