US Patent 9454133 Timepiece calendar mechanism

Watch comprising a movement arranged to drive a timepiece calendar mechanism, which includes drive means that drive, at each change in month, complementary drive means arranged to drive a month cam whose periphery cooperates with a month feeler arm comprised in the calendar mechanism, where this month cam covers an angular sector of less than 360°, and the calendar mechanism includes elastic return means arranged to instantaneously return the month cam in a backward movement, in cooperation with the month feeler, to the position of the first month of the year upon completion of the last day of the preceding year.