Bad news, everyone: Birthday wishes might clutter your Facebook newsfeeds today more than usual.

That’s because September 16 is the most common birthday in the country, with summer months reporting the highest number of babies born, according to a Harvard study.

‘I’ve always noticed this seasonal birth pattern, and one thought is that people just have less sex in warmer months because it’s so hot out.’ - Mary Jane Minkin, clinical professor of gynecology

So if that happens to be your birthday, well, happy birthday! And if your Facebook feed isn’t evidence enough, know that you probably had a lot of company in the maternity ward on that fateful day.

Nick Jonas, Amy Poehler and Alexis Bledel are just a few of many celebrities blowing out their birthday candles today.

While September 16 may hold bragging rights on this account, the most common birth month overall is August, based on the study’s data from 1973 to 1999. July comes in second.

Researchers don’t know for certain why late fall and early winter promote rampant baby-making, but they have a few guesses..

There are some scientific theories: A 2013 study suggests that hot weather impacts sperm quality, while length of daylight affects how well women’s pituitary-ovaries work.

But even science leaves enough room to speculate that “increased sexual activity associated with end-of-year holiday festivities” could play a role. Happy holidays, indeed.

Other experts say that the stifling, please-don’t-come-near-me summer heat might also explain the sweatier half of this trend.

“I’ve always noticed this seasonal birth pattern, and one thought is that people just have less sex in warmer months because it’s so hot out,” Mary Jane Minkin, clinical professor of gynecology at Yale School of Medicine, told Yahoo News.

And then, as far as least popular birthday goes, it shouldn’t take a lot of guesswork to figure out. Poor February 29, the leap day that comes around only once every four years, ranked dead last for birthdays in the country since it has always struggled to measure up to the “real” days.

To see how your birthday ranks, check out this infographic from the Viz Wiz.