I was reflecting this leap day on how weird and awesome leap days are. They exist just to keep the seasons from shifting around the calendar, which is what used to happen when we didn’t adjust for how the year isn’t exactly 365 days long. But it’s remarkable to me how simple it is to implement them nowadays: since the year is almost exactly one quarter of a day longer than 365, we just need an extra day about every four years to count that extra time.
I don’t think it’s widely known, but the year is actually just a little less than a quarter day longer than 365 days. Adding an extra day every four years is a slight overcorrection, and the drift accumulating since its inception in the Julian calendar in 46 BCE became intolerable by the 15th century because by then Easter was coming ten days early.
The solution in the Gregorian calendar was to skip leap day three times in 400 years: years divisible by 100 aren’t leap years unless they’re also divisible by 400. Since it was adopted in 1582, that meant the first skipped leap year in the Catholic world wasn’t until 1700 (and protestant England refused to adopt a Catholic innovation at all until 1752). We millennials didn’t get to enjoy any of this fun since 2000 was still a leap year, but that year was remarkable in that it was only the first business-as-usual leap year observed in a century year since we started occasionally skipping them. I only know about any of this because it’s intro programming practice to compute whether a given year is a leap year or not.
That got me thinking about how much the world has changed since the last leap day. On February 29th, 2020, China was already in full meltdown from a novel coronavirus, but Italy was still more than a week away from its own first-in-the-west nationwide lockdown. Since then, we’ve also had a riot in the Capitol, Elon Musk nearly killed Twitter, and there have been not one but two world-changing invasions ostensibly over ancient claims to land in the east. But in happier developments, the finest space telescope in history got born without a hitch, there’s new American hardware on the moon for the first time since Apollo 17, and we’ve hit a real cultural turning point with rapid advancements in generative AI.
Closer to home, the last four years have seen huge changes for the Brewsalas, too. We doubled our number with Zelda and Felix, I changed jobs twice, and we moved 650 miles to the south in between all that! But the more things change, the more they stay the same: I was astounded to notice that our house in California is virtually due south from our house in Washington, further east by less than one fortieth of one degree of longitude.
Here’s to another four years before we get another extra day! Something tells me the pace isn’t going to slacken.
