In a bit of a break from heavy topics, we’re going to look at why February is so weird. The average month is 30.4 days, sensibly splitting into either 30 or 31. A seven-to-five distribution of 30-day months and 31-day months would get most years right, or an even split gets leap years. Why, then, does February jump the shark to 28? The weirdness doesn’t stop there, because in every year divisible by four February has 29 days: still unique among months. Yet this special treatment does not apply to century years. Except every 400 it does. February is the month that takes up all the slack in trying to fit a rigid integer-based system onto a more nuanced reality. And the choice of February is not entirely arbitrary. It would make less sense to abuse June or August in the same way, for reasons we’ll address.

All of this was inspired by equinoxes (thus the timing of the post: equinox happens Friday). More viscerally, all this was inspired by lengthening days. Living at latitude 48°, the days here go from just over 8 hours long to just over 16 hours long through the course of the year. Around this time, it’s quite dramatically noticeable how quickly day length is changing—by almost a half-hour per week at my latitude.

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