On seasonal crepuscularity and pseudo-saint Seculus

Because I am sensitive to the waning of the sunlight in the winter, I am always happy to welcome its return. Most years I use this space to call out the day of the year on which the sun sets the earliest. This usually happens around December 9 at my latitude. If you’re wondering why it doesn’t happen on the shortest day (the solstice, December 21st), I tried to explain it carefully last year.

I’ve always felt this day, being special, should have a special name, but I could never come up with anything I liked. So I was amused to see that someone else with strong feelings on the subject has proposed just such a name. A Dr. Richard Wilk, in a letter to the Philadelphia Inquirer (philly.com), proposes that we call the day Seculus, where the name suggests that it has nothing to do with religion. What do you think? I’m game. I like the notion of Seculus as a god who refuses to believe in his own existence. And for this act of reasoned restraint, we give him his own saint’s day. The blessings of Seculus upon you!

Now the interesting thing about Seculus is that it varies by latitude. The farther north you go, the later it occurs. As such it provides a sort of perpendicular counterpoint to New Year’s Eve. Because everyone on a single meridian celebrates midnight at the same stroke, we are conjoined in longitudinal fraternity. Seculus, on the other hand, unites us with our latitudinal brethren. Are you on Latitude 42? If so, you are my Secular Sibling, and December 9th is our festal day.

Accordingly, last month I wanted to illustrate exactly when, by latitude, the earliest sunset occurs but alas I didn’t get my act together in time. But now, with the help of some code from the U.S. Naval Observatory I can present a chart that is still timely: the latest sunrise by latitude.

The latest sunrise occurs on the far side of the solstice, as you might suspect. At my latitude it happened about a week ago. Since I am not a morning person, I propose no special holiday for the latest sunrise. But you seasonal affective early risers may disagree.

And here, to complete today’s story, is the Seculus Succession, being a chart of the timing of that noble and moveable feast.