The invention concerns a lunar month display mechanism, for a lunisolar calendar mechanism. The mechanism includes concentrically a plate, which determines the position of the additional month in the bissextile years. The plate is provided with a hand associated with a scale of twelve months and carries a planetary wheel permanently braked by a restraining device. The drive wheel, driven over one twelfth of a revolution at each new moon, meshes with the planetary wheel and moves the plate and hand forward. At the start of a bissextile month, the stop fingerforces the wheel to rotate overcoming the force of the restraining device while the drive wheel is rotating, such that the hand remains close to the number of the preceding month. The position of the stop finger is determined by a year cam. This mechanism can be used in particular in a Chinese calendar display.