Religion has a 50-50 chance of being correct. Many religions that we know about oriented things towards mid-winter and mid-summer.
Of course, I think the last bit of light may be equally valid. The question remains, though; why the last bit of light on that particular day?
If you believed the official commentaries on just about all discoveries, you would believe all of them to be important religious revelations about the lives of ancient people. After years and years of hearing the same old line, you might conclude that ancient people, spending well over 95% of their waking time on survival in a hostile world, still had time to be the most religious people in history.