Yitai- as I wrote. I was discussiing the term “kofer’ which means, “deny-er”and the quesiton was, what does one deny? After Sam2 pointing to the Rambam, it is clear that the Rambam-at least- considers someone a “kofer’ if he denies the origin of torah shebaal peh-misinai. I also said that i am pretty sure president peres is a classical “kofer’ in any case, because idobut he even accepts torah sh bi ksav -misinai.
All that said, to say that the world is older than 5762 may not be kefirah at all- as there is dispute, even amongst rishonim- how to interpret maaseh bereishis.
As far as our count- it comes from seder olam- a midrashic text and if you look carefully, you will see that signs of civilization started- virtually everywhere- about six thousand years ago.