Annual or perpetual calendar mechanism, comprising - a day-of-the-month mobile which is rotational between 31 successive angular positions each associated with one of 31 days of the month and which comprises a notch and a day-of-the-month wheel having 31 teeth (61, 62, 64), - a month mobile which is rotational between successive angular positions each associated with one of the 12 months of the year, which comprises a month wheel having as many teeth as the month mobile has angular positions and which defines course beginning stops each associated with a month and operational for controlling a course beginning position when the month mobile is in the angular position associated with this month, - an actuation finger for effecting, on one of the teeth of the month wheel, an actuation of one step making the month mobile pass from one month to the following month, at each passage of the day-of-the-month mobile from the last day of the month of one month to the first day of the month of the following month, - a lever provided to be actuated once a day, starting from the said course beginning position, - a manoeuvring device (22, 45, 49) borne by the lever and comprising two pawl fingers, namely • a first pawl finger for effecting, on one of the 31 teeth (61, 62, 64) of the day-of-the-month wheel, an actuation of one step making the day-of-the-month mobile pass from one day of the month to the following day of the month among its 31 successive positions, at each actuation of the lever, and • a second pawl finger for effecting, on the notch, an actuation of the day-of-the-month mobile by a whole number of steps determined by the course beginning position of the lever, at the time of an actuation of this lever at the end of a month of fewer than 31 days, each of the 31 teeth (61, 62, 64) of the day-of-the-month wheel having a profile that a peripheral edge of this day-of-the-month wheel forms, characterized in that the peripheral edge of the day-of-the-month wheel also forms the said notch which is positioned between two consecutive teeth (61, 64) among the 31 teeth (61, 62, 64) of the day-of-the-month wheel. - a day-of-the-month mobile which is rotational between 31 successive angular positions each associated with one of 31 days of the month and which comprises a notch and a day-of-the-month wheel having 31 teeth (61, 62, 64), - a month mobile which is rotational between successive angular positions each associated with one of the 12 months of the year, which comprises a month wheel having as many teeth as the month mobile has angular positions and which defines course beginning stops each associated with a month and operational for controlling a course beginning position when the month mobile is in the angular position associated with this month, - an actuation finger for effecting, on one of the teeth of the month wheel, an actuation of one step making the month mobile pass from one month to the following month, at each passage of the day-of-the-month mobile from the last day of the month of one month to the first day of the month of the following month, - a lever provided to be actuated once a day, starting from the said course beginning position, - a manoeuvring device (22, 45, 49) borne by the lever and comprising two pawl fingers, namely • a first pawl finger for effecting, on one of the 31 teeth (61, 62, 64) of the day-of-the-month wheel, an actuation of one step making the day-of-the-month mobile pass from one day of the month to the following day of the month among its 31 successive positions, at each actuation of the lever, and • a second pawl finger for effecting, on the notch, an actuation of the day-of-the-month mobile by a whole number of steps determined by the course beginning position of the lever, at the time of an actuation of this lever at the end of a month of fewer than 31 days, • a first pawl finger for effecting, on one of the 31 teeth (61, 62, 64) of the day-of-the-month wheel, an actuation of one step making the day-of-the-month mobile pass from one day of the month to the following day of the month among its 31 successive positions, at each actuation of the lever, and • a second pawl finger for effecting, on the notch, an actuation of the day-of-the-month mobile by a whole number of steps determined by the course beginning position of the lever, at the time of an actuation of this lever at the end of a month of fewer than 31 days,