Tell Time The Cistercian Way

It’s rare for the fields of the engineer and the mediaevalist to coincide, but there’s a clock project bringing the two fields together. The Cistercian monastic order used an intriguing number system from the 13th century onwards that could represent any four-digit number as a series of radicals expressed in the four corners of a single composite symbol, and it’s this number system that’s used by the clock to render the full range of 24 hour time on a large 5×7 LED matrix mounted on a wooden base.

Behind the scenes is an Arduino and a DS3231 real-time clock, and all the code can be found in a handy GitHub repository. There’s even a PCB from everyone’s favourite vendor of purple PCBs, The result is certainly an interesting clock that makes the break from the usual binary and Nixie timepieces with some style. It also provides an introduction to this fascinating but obscure numerical system, in the event that any of us might have missed the one other such clock that has made it to these pages.

10 thoughts on “Tell Time The Cistercian Way

    1. And most of those 35 LEDs are not even functional. Only 24 are used, and only 16 are actually required.

      On the other hand, with an even simpler (binary) scheme, you can unambiguously specify every second in a year with just 25 LEDs. Though, admittedly this scheme does impose a modest increase on your wetware’s computational burden to convert, say, 10 am local time to 25 bit binary.

      Or, heck, just go the full 32 bit unix time. Some folks natively think in that already.

  1. It bothers me immensely that the pattern for ‘6’ is inconsistent with the rest of the scheme. It seems very un-monk-like.

    6 should be to 5 as 4 is to 3.

    I’m very sorry if you can’t unsee that now.

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