Originally Posted by Cat Herder:
My thoughts, soon to be disproven I expect, are with human breeding cycles. 
Winter is when most humans are focused on infants, children and family. The holidays keep the focus there. We do it for a biological reason. Even if we don't want to see it. By summer, most are focused on other things. In EMS we call summer gunshot season because of the number of those calls we get during that time. Short tempers, domestic violence and breakups seem more common.
Harvard sort of agrees, although does not link up the two issues. 
"Most animals mate at a certain time of year. One of our evolutionary advantages is we can continuously mate and have young. However, if you look at birth patterns, you’ll notice that most birthdays tend to occur at certain times of year. For a mammal with no official mating season, it’s surprising that the majority of births occur between July and September. September is the most common birth month in the US, according to one Harvard study, with September 16th being the most common day. Count back the months and you’ll realize that these babies were conceived around the holidays."
https://bigthink.com/philip-perry/wh...-we-do-sort-of
I have a child with a Sept 16th birthday hahaha