Ahh, back in the good ol' days when teenagers didn't know it all.
Both have their entrance passage pointing in the same direction, so that on Mid-winter's day, the rays of the setting sun point right down the passage.
Of course it was all about religion and didn't have anything to do with trying to get the last bit of light inside in the days before electricity.
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?