We make a lot of things this time of year. Gingerbread houses. Christmas cards. New traditions. Babies.

Yes, December is peak baby making season. It’s a month filled with togetherness and all the love felt in December is what makes September the most statistically popular month for American birthdays.

According to data journalist Matt Stiles, mid-September is the most popular time to give birth in America. He did a deep dive into the birth stats from the U.S. National Center for Health Statistics and the U.S. Social Security Administration collected between 1994 and 2014 and found that the most common American birthdays fall on September 9, 19 and 12. In fact, 9 of the 10 most popular days to give birth fall in September.

If we turn the calendar back, we’re looking at Christmas time conceptions. Stiles illustrated his findings via a heat map, which presents the data in a visual form. The darker the square, the more common the birthday.

The square for August 30 is pretty dark as it is the 34th most common birthday in America. It’s also 40 weeks after November 23, and the unofficial beginning of the United States’ seasonal baby boom.

And while the Christmas holidays are common times to conceive, they’re not common days to give birth, for obvious reasons. Christmas Eve, Christmas Day, New Year’s Day and the fourth of July are all represented by light squares on Stiles’s data map, meaning they’re among the least popular days to welcome a little one into the world (Boxing Day is just a smidge darker, still a pretty rare birthday).

OB-GYNs are not likely to schedule C-sections on major holidays, so that might point to the low birth rates on these special days.

As for the September baby boom, it probably has less to do with the magic of the holiday season and more to do with the fact that many Americans take time off work during the holiday season. It’s not that mistletoe is some magic aphrodisiac, but just that making babies takes time, and at this time of year we have some to spare.

This Christmas be thankful for the time you have with your loved ones and your partner. That time could give you a gift come September.

[A version of this article was originally posted November 21, 2018]