Date mechanism comprising a display crown with an internal tooth arrangement carrying day-of-the-month indications ranging from one to thirty one and intended to be designated in succession in order to indicate the day of the month, one tooth of the internal tooth arrangement of the display crown being replaced by a drive member of a different shape to that of the teeth of said tooth arrangement, a month cam, the angular position of which is indicative of the number of days in the current month and a lever comprising a feeler spindle and a pawl, said lever being intended to be rotationally driven from a position in which its feeler spindle abuts against said month cam, this position depending on the number of days in the month, to a predetermined position, the whole being arranged so that: - whatever the number of days in the current month, when the day of the month is between one and twenty nine inclusive, upon each rotation of the lever from the position in which its feeler spindle abuts against the month cam to said predetermined position, the pawl cooperates with a tooth of the internal tooth arrangement of the display crown to drive the rotation by one step of said display crown, the designated day-of-the-month indication thus being incremented by one unit; - when the day of the month is thirty: ∘ if the current month is a thirty-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam, the pawl cooperates with a first part of the drive member to drive the rotation of said display crown by a first step, then cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the display crown by a second step, the designated day-of-the-month indication thus passing from thirty to thirty one, then from thirty one to one consecutively; and ∘ if the current month is a thirty one-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam to its predetermined position, the pawl cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the rotation of said display crown by one step, the designated day-of-the-month indication thus passing from thirty to thirty one, - when the day of the month is thirty one, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam to its predetermined position, the pawl cooperates with a second part of the drive member to drive the rotation of said display crown by one step, the designated day-of-the-month indication thus passing from thirty one to one. - whatever the number of days in the current month, when the day of the month is between one and twenty nine inclusive, upon each rotation of the lever from the position in which its feeler spindle abuts against the month cam to said predetermined position, the pawl cooperates with a tooth of the internal tooth arrangement of the display crown to drive the rotation by one step of said display crown, the designated day-of-the-month indication thus being incremented by one unit; - when the day of the month is thirty: ∘ if the current month is a thirty-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam, the pawl cooperates with a first part of the drive member to drive the rotation of said display crown by a first step, then cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the display crown by a second step, the designated day-of-the-month indication thus passing from thirty to thirty one, then from thirty one to one consecutively; and ∘ if the current month is a thirty one-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam to its predetermined position, the pawl cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the rotation of said display crown by one step, the designated day-of-the-month indication thus passing from thirty to thirty one, ∘ if the current month is a thirty-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam, the pawl cooperates with a first part of the drive member to drive the rotation of said display crown by a first step, then cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the display crown by a second step, the designated day-of-the-month indication thus passing from thirty to thirty one, then from thirty one to one consecutively; and ∘ if the current month is a thirty one-day month, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam to its predetermined position, the pawl cooperates with a tooth of the internal tooth arrangement of the display crown adjacent to the drive member to drive the rotation of said display crown by one step, the designated day-of-the-month indication thus passing from thirty to thirty one, - when the day of the month is thirty one, under the effect of the rotation of the lever from the position in which its feeler spindle abuts against the month cam to its predetermined position, the pawl cooperates with a second part of the drive member to drive the rotation of said display crown by one step, the designated day-of-the-month indication thus passing from thirty one to one.