bs22fly
1535
Calendrier Date Wheel
Sorry for the late response but I just finished moving to Hong Kong and it's been a bit crazy.
"The date-hand rides up its scale on the curve of a snail cam mounted on the date-wheel. On the last day of the month, the date lever drops to the bottom of the cam, to bring the date-hand flying back to the start to its scale. The date-hand itself is moutned on the pinion between two racks, one of which incorporates a blade-spring. The racks hold the date-hand precisely to the number on its scale, while controlloing its return when the lever falls down the cam."
As a result of being connected to the wheel you can see why it begins to move foreward prior to the hour. The Calendrier is not the only Annual Calender that has all the functions set by the crown. The MIH watch made by Ludwig Oechslin is also set by the crown. UN also makes a perpetual that's set by the crown. Maybe others know some more.
Others have discussed with FPJ about making a perpertual. He didn't seem very interested. I think some version of an equations of time would be more likely 
This message has been edited by bs22fly on 2007-09-11 07:04:47