Years ago I taught a “math for poets” class. (I don’t remember the actual name of the course. Everyone called it “math for poets” because it was the one math class humanities majors had to take.) I taught the students how to mentally figure out days of the week and they loved it. It was easily the most popular topic in the course. It was satisfying to find any topic that was popular in a course that many had put off as long as possible.

I’d thought about turning my old class notes into a blog post, but there’s one minor complication. I taught this course in the 1990’s and the method was designed to make it easiest to work with dates in the 20th century. You could use it to compute days of the week in the 21st century, but doing so would take one more step than revising the method to make it easier to work with 21st century dates. I recently ran across an article that gives such an updated method.

## 4 thoughts on “Computing days of the week in your head”

1. Great stuff! My university is embarking on a massive quantitative literacy project and it’s hit-or-miss figuring out what will catch the students’ imagination. This might do the job, especially for the historians and social scientists.

You never know what interest students. For example, when I taught probability to EE’s, they were totally un-enthused–until I introduced entropy and showed them how to construct Huffman codes for simple data compression. Then the course caught fire and the students were in to everything. Go figure.

2. “You never know what interest students.” Absolutely.

Once when I taught a course on differential equations for engineers, they whined about the chapter on mechanical and electrical vibrations, the only part of the course they’re likely to ever use. They were eager to get past applications and go back to solving abstract equations.

In the “math for poets” class I spent one day describing how musical instruments work: harmonics etc. On the course evaluations that semester, I got several comments specifically about that topic. Some students said it was their favorite. Others asked why I wasted their time in a math class talking about music.

3. This turned into a great non-recursive Klein program. Thanks! ðŸ™‚

“Some students said it was their favorite. Others asked why I wasted their time…” This is one of the great mysteries of teaching — and one reason not to overemphasize
any particular student feedback.