My university degrees were in Medieval Studies. In recent years I haven’t had much cause to crack open a manuscript, but the recent visit of a scholar friend from overseas got me thinking of an old puzzle I hadn’t solved yet.

Manuscript 01020 is housed in the Thomas Fisher Rare Book Library in Toronto. Most of it is devoted to a notabilia Bible, that is, a collection of quotable quotes from scripture suitable for inclusion in fifteenth-century business or government correspondence. However, it has a few interesting miscellaneous folios too. One of them is a single page of fencing instructions and another one is a list of unlucky  days of the year. A third one is mysterious calendar.

When I first looked at the calendar a few years ago, I couldn’t figure out how it worked, but now that I’ve returned to the puzzle, I think I’ve solved it. It doesn’t require a degree in astrophysics to understand, but you do need to know that the manuscript was probably made in Florence. Click on the photo to see a larger version of the image. Can you see how it works?

Here’s a hint: by medieval Florentine reckoning, numbered years begin in March.

I’ll post an answer at a later date, when people have had a chance to grapple with the puzzle.