... I will definitely try to pick up a copy of that deCarle book. Does anyone know if it is safe to advance time over midnight if just off by a day or two and will that move forward the perpetual calendar? Guess that could be a pragmatic although time-consuming solution.

I am very fascinated by the design and the function of the early Patek perpetual calendar watches (e.g. 1526 / 1518). At the same time I am wondering how "practical" they really are. I suspect nobody is wearing such a watch on a daily basis and even winding it every 24 or 48 hours or so will often b