Perpetual calendar with a differential mechanism

A perpetual calendar mechanism for a timepiece including a timepiece movement arranged to control the daily release, at the moment that the date changes, of a mechanism actuating a perpetual lever comprised in said perpetual calendar mechanism, wherein said perpetual calendar mechanism includes a calendar mechanism, a daily countdown mechanism which includes a month-end adjustment mechanism, and a differential mechanism, wherein said calendar mechanism is arranged to determine the duration of the current month and is updated at each change of current month by said daily countdown mechanism, and wherein said differential mechanism is arranged to control, each day at the moment that the date changes, the motion of an additional adjustment cam comprised in said month-end adjustment mechanism, based on information on the current day of the month taken from said daily countdown mechanism, and information on the current month duration taken from the calendar mechanism.