“I feel Kennedy was one of our finest Presidents, especially in the 19th century.”

This is not a writing error. I’d like to say it’s not a thinking error either, since so many of my students find the ordinal naming of centuries mystifying…but the sentence was written in the same century as Kennedy’s presidency, so I have to wonder whether my student thought she was living in the 19th century also. Or perhaps the first half of the 1960s, some two decades before she was writing, seemed so hopelessly remote as to have been a hundred years past. Come to think of it, President Kennedy was assassinated before this student was born: it might as well have been a hundred years ago, I guess, as far as she was concerned.

But that logical riff is probably just self-indulgence on my part. I really think she meant the 1900s, a correct choice, and just thought that the first two digits of the year should correspond to the number of the century.

Why is this so hard? My student’s error is unique in my book for its placement of JFK’s presidency in the middle of Lincoln’s (and I am just now realizing how astonishing a juxtaposition that is), but she is only one of many, many students who have been confused by the way we count time.

I did go through a brief period of confusion myself, back in junior high, when I had trouble remembering whether to add or subtract when converting year to century: was 1776 in the eighteenth century or the sixteenth? I already knew it definitely was not in the seventeenth. But I learned to keep the counting straight thanks to a teacher who asked what century the years 1 to 100 belonged to, inviting us to realize that there couldn’t have been a zeroth century. So, a mental reminder that to get the right number of a century one had to add 1 to the date’s beginning number has served me pretty well ever since—if I have to think about it at all.

But the same reasoning or mental reminder, or an equivalent memo to the brain, doesn’t seem to have lodged as reliably in the minds of my students. So I have developed the perhaps-annoying habit of tagging the years onto the century when I talk in class: “In the eighteenth century (that is, the 1700s)….” I hope that for much of my audience this clarification is unnecessary; but I know that for some of the wrinkled brows out there, it is useful, or even needful, every time.

Are we dealing in this instance with only one proof of our innumeracy as a culture, or are references to time confusing in a unique way? “Century” is a vague but weighty term. I recall a teacher in high school who one day asked us if we thought any of us would live to see the twenty-first century. It did seem like the remotest of possibilities, because from the vantage of the twentieth century (our “time”) the twenty-first was a hundred years away. A bit of arithmetic revealed that the students, at least, had pretty good odds of making it (only another 38 years or so), and in all likelihood so did the teacher—but at the tender age of 17, even 38 years seems a pretty long time, and a teacher aged 40 quite a fossil and one aged 78 an impossibility. A couple of decades later, though, some of my own students thought of the twenty-first century as still far off in the future, even though 18 was a number easier for them to conceptualize. Or was it? Eighteen years was, for them, a “lifetime,” which is another word meaning a long, long time. And when I say “in the twentieth century” now, even though my students were themselves born in the twentieth century, I know I should add the word “back”—back in the twentieth century—if I want to accurately reflect the remoteness of that time.

So is “century” a word that connotes something other than actual years? If so, perhaps we shouldn’t be surprised when people can’t quite match up the round number and the date. Is it too much to ask, nevertheless, that students who have trouble with the concept make a mental note of the solution?

Isn’t that what people do? I myself have trouble remembering which direction is “left” or “right,” for example, and being a stage director as well means that “stage right” and “stage left” rush in to complicate matters even further. So in “real” life, I confess, I mentally Pledge Allegiance sometimes to confirm which is my right hand; and when blocking a play, I label “SR” and “SL” on my stage diagram as an aide-memoire.  That is, if you know you have an intellectual blind spot, you get a mental guide dog to help you navigate it.

Is there a guide dog who can help with labeling centuries? Or is Kennedy stuck forever in the Civil War?