I have always liked Leap Year, and I find it unfortunate that it doesnât get the proper celebration itâs due. I feel that Leap Day should be an international holiday! After all, itâs relatively unreligious (itâs rooted in the Gregorian calendar, which despite being widely adopted across the planet for commerce and diplomacy is still of Christian origin...), is unattached to any specific ethnicity or culture, and affects the entire planet.
Americans seem to go out of their way to co-opt holidays they have no business celebratingâCinco de Mayo, or St. Patrickâs Day for instance, not to mention invented holidays such as the Super Bowl, or ones that celebrate dubious individuals, such as Columbus Day. And yet, we let Leap Day pass as hardly more than a little extra packing before March.
Leap Year happens because the cycle of the Earth around the Sun is 365 and a quarter days. Thatâs how long it takes for the earth to return to the same physical position in relation to the sun. But a quarter day is an inconvenient thing to mark on a calendar, especially because the rotation of the Earth on its axis doesnât care about the rotation of the Earth around the sun. So our calendar is rounded down to 365 days. But if every year were marked as only 365 days, our calendar would slowly get out of sync with the seasonsâJanuary would head towards Autumn, while July crept back towards Spring. Every four years we add a day to the calendar to reset the phase shift.
Itâs my kind of holidayâessentially inconsequential and unimportant, but quirky and necessary. It falls at the intersection of our particular location in the universe, and our own human culture with our particular ways of recording time. Itâs unique to us as Earthlings, and even more so to us as humans. And on top of that it only happens once every four years! Whatâs not to celebrate?
Back in the year 2000, my dad told me that this Leap Year was extra special because Leap Years donât happen in years that are multiple of 100, unless itâs a multiple of 400âan extra accommodation of math to maintain seasonal accuracy. I remember lamenting in my journal at that time that I had missed the opportunity to write in said journal on 2/29/00 because it was a once-in-400-year opportunity to experience such a Leap Day.
Years later, it occurred to me that this Leap Day century thing was something Dad invented, and I had mistakenly believed it for years. This was right around the time I was discovering a lot of things Dad had told me as a kid were in fact invented, not maliciously, just jokes about the workings of the world that I was too young not to take at face value. This fell right in line with thoseâit just didnât seem to make sense.
Last Leap Year, I was researching the origins of Leap Year, and I discovered that he didnât invent it. Itâs true!
I told you that the a full solar orbit isnât 365 days, but actually 365.25, but actually actually itâs 362.2425 days long*, or about 11 minutes shy of 365-and-one-quarter days. Even with our Leap Year accommodation, we would still get out of phase with the seasons (albeit very slowly) by gaining three extra days every 400 years. To account for that, every 100 years we donât mark Leap Year, but on the 400th year we do.
What makes this Every 400 Years Leap Year so special (and thus, even further up my alley of inconsequentiality) is that itâs not special. Itâs marked like every other Leap Year, even though it only happens every 400 years. Itâs significant by being ordinary. As a lover of Leap Year as I am, I was thrilled to discover that I did in fact experience a once-in-400-year occasion! And to discover this on Leap Day felt like the perfect way to celebrate.
This year Iâm celebrating Leap Day by spreading my enthusiasm about Leap Year. So happy Leap Day!
*Ok, actually actually actually the full orbit is 365.2422, but that difference of .0003 days creates a phase shift so slowly that it hardly matters to humanity. After 1,000 years weâll be off by not even 8 hours. Humans and our calendars will be long dead and gone before any noticeable seasonal shift happens.