a train of clockwork with perpetual julian date , characterized in that it comprises an adjusting device for causing a date indicator to carry out adjusting steps , for automatically taking into account months with 28 , 29 , or 30 days , said adjusting device comprising a rotating cam driven at least one step every twenty - four hours , said cam having an outline for controlling a sensor bringing about : the oscillating motion of a mobile element provided with a click spring system , for moving forward the date indicator by the required supplementary step , and the forward movement of said cam for causing it to make the number of steps equal to the number of adjusting steps of said indicator for carrying out one complete round every year .