No. Not a year, Month, week, day, hour or minute. Is that what you are looking for? If so, to what purpose?You can't pick a point in time when people started rejecting God?
Another thing to consider in the migration away from belief was the folly of monotheism itself. It took all the forces that pagans were worshipping separately, the different aspects of nature, the fates, etc... and consolidated them into a singular focused God that they continued to try and define and refine to fit their witnessed experience. It made it easier to isolate and discard as it was found that the definitions and apologetics surrounding this now singular phenomenon continually failed the smell test of real experience.