Kalends, Calendars, and Intercalation

Our word calendar comes from the Latin word kalendae, or kalends, which named the first day of the month. (For a while, Latin used k instead of c before the letter a. Try not to pay attention to this right now. We have more serious obstacles ahead.) Those wacky Romans didn’t number the days of the month consecutively as we do, 1 to 30 or 31, but instead named three days of the month, based on phases of the moon, and counted the days backwards from those dates. Hence, the last day of November was not November 30 but the day before the kalends of December, or, pridie Kal. Dec. November 29 was the third* day before the kalends of December, or, ante diem III Kal. Dec.

Today, Wednesday, November 23, is ante diem IX Kal. Dec., the ninth day before the Kalends of December.

Are you still with me?

In this tripartite division of the month, the Nones fell about a week after the Kalends. Then came the Ides, which Julius Caesar’s assassination made famous (“Beware the Ides of March!”) It landed about the middle of the month.

There’s plenty more to say about this demented timekeeping, but you’ve probably had enough. If you want to know more, look here.

From my recent reading, I learned yet another derivative from kalendae. To intercalate is to insert a day into a calendar. You can see the connection to calendar, plus the prefix inter, meaning “between.”  The Romans used to intercalate days in February to adjust the calendar, which would get out of whack every few years. After Julius Caesar’s calendar modifications in 46 BCE, we have only one intercalation, February 29, every four years. We still rely on the Julian calendar.

Once again, the scientists among you are probably way ahead of me. A scientist, in fact, set me on the path to this convoluted post. Catherine Raven, a biologist, uses the word intercalation in her memoir Fox & I: An Uncommon Friendship, but in a different sense. In its non-calendar sense, intercalation can relate to inserting new elements or layers into a substance or system. In chemistry, a “guest molecule,” as it’s courteously called, can be introduced, or intercalated, into a compound. An editor can intercalate new chapters in an old book. In geology, layers of sediment are sometimes said to be intercalated.

Huh, I thought, when I had progressed about halfway down this rabbit hole. Kalends must have more to it than the first day of the month. I had never investigated the etymology of kalends. Turns out kalends derives from the Latin verb calare, “to announce.” Roman priests, observing the new moon, solemnly announced the kalends of every month from the Capitol. The original kalends were the announcement itself.

Announcing a day (calare) gave rise to kalends, the first of the month, which gave rise to calendar, which gave rise to intercalating (inserting days into a month), which gave rise to a more general intercalating (inserting something into something), such as intercalated discs in cardiac muscle or, you know, the intercalation of copper atoms into transition metal dichalcogenides.

So let me know. For next Wednesday, choose whether we should:

1. Take a deeper dive into the Roman calendar;
2. Examine the etymology of dichalcogenides;
3. Find out why it’s not really insulting to write Xmas instead of Christmas;
4. All or none of the above.

*Why the III (three)? The first day of the month was regarded as “1.” The day before that was #2, the pridie. The day before that was #3. I know, right?