25 years ago, when I started work in Bolsover (UK) I had the privilege to meet Mr Harrison (no relation to The Mr (Chronometer) Harrison. Mr Harrison had been the local Jeweller and early last century had designed a perpetual calendar which could be added to the movement of a clock. It was extremely simple with only 6 moving parts it would give the day of the week, date and month even taking into account leap years without any further adjustment. He sold the design to Smith Clocks who were tooling up to produce clocks with this when the Second World War broke out.
I enclose pictures of a clock he made himself which I have recently acquired. His son tells me that he also added smaller versions of this calendar to 2 watches, both he and I would love to know where these are now.
The calendar drive rake is driven by a reduction gear coming out of the front of the movement and its arms are adjusted by cams and grooves in the plastic (Tuffnel) rings which are also moved round by it with the dates etc on their front sides.
Mr Harrison died some years ago. I think he was a brilliant man.