Annual calendar mechanism for a timepiece

An annual calendar mechanism for a timepiece, such calendar displaying through a window pierced in a dial or by division marks applied to the dial to which a hand points, such mechanism including a date driver wheel set making one revolution in twenty-four hours, said wheel set being fitted with at least one finger adapted to drive a date wheel including thirty-one teeth through one step once each day, said date wheel operating the calendar display, the date wheel driving an intermediate wheel including thirty-one teeth, thirty of which are truncated, the non-truncated tooth driving a first plate of an annual wheel bearing twenty-four teeth once per month through two steps, such annual wheel comprising a second plate fixed thereto and superposed thereon bearing five teeth, each corresponding to months of less than thirty-one days, each of such teeth being arranged so as to come into the path of the finger of the date driver wheel set at the end of the cited months so as to drive the annual wheel through one step, which has as consequence the driving of the date wheel through an additional step via said intermediate wheel at the end of said months.