American Calendar Clock (perpetual)
Ithaca Calendar Clock Company, Ithaca New Yersey. Ca. 1870.
Image 1. This clock features a separate dial that shows: day of week, date,
and month (i.c. sunday 17th november). The mechanism keeps track of the length
of the months, and even knows when to skip februari 29th and when not. This
function is called "perpetual date" and is very rare. For this function, there
is a part inside the clock that takes 8 years to revolve one time!