I mean, if God wanted mankind to know the date of the creation of the first man, He could have made that much clearer in Genesis. That would've had the additional benefit of giving the whole world a basis for a starting calendar year. January 1, 1 would be the year humanity came into existence. I think it's a pretty good starting point.
(I know, I know... he wouldn't have named it January. Maybe he could have improved on the names of months, too!)
While God was at it, he could have made the earth go around the sun evenly. Instead of 365.25 days, he could have made it an even number. It is almost as if things just came to be without the direct influence of a god.