In an annual or perpetual calendar mechanism, a day-of-the-month wheel includes a notch. At each actuation of a lever, a first pawl finger effects an actuation of one step, on one of the teeth of the day-of-the-month wheel. Upon actuation of the lever at the end of a month of fewer than 31 days, a second pawl finger effects, in the notch, an actuation of the day-of-the-month wheel by a whole number of steps. The notch is positioned between two consecutive teeth among the teeth of the day-of-the-month wheel. The day-of-the-month wheel has a peripheral edge which forms the profiles of its teeth as well as the notch.