The present invention concerns a watch having time-setting means and a calendar mechanism comprising a lever loaded by a spring and released once a day from a 24 hour wheel, which is driven by the watch movement to complete one revolution per day, the effect of the release of the lever being to move a date wheel set, for example including a star wheel, forward one step in the calendar mechanism.
The invention applies in particular, but not exclusively, to a so-called instantaneous date watch, wherein the calendar mechanism comprises a spiral shaped cam, secured to the 24 hour wheel and acting on the lever to wind it progressively during one day against the lever spring, a click provided with a return spring tending to set it in a stop position in which the click restrains the lever in the wound position against the lever spring, and a release finger arranged on the 24 hour wheel to act at a determined time on the click such that the latter releases the lever. This type of calendar mechanism arrangement has the advantage of moving the date wheel set forward instantaneously, for example each day around midnight owing to the action of the 24 hour wheel, so that the date and day indicators give correct indications before and after midnight. Such mechanisms are well known and the reader can find a description thereof in Swiss Patent No. 1018 for example.
In conventional calendar watches, when one moves the hands manually in order to set the time of the watch, for example because it has stopped, the 24 hour wheel can pass through its midnight position and activate the calendar mechanism by incrementing the date and the day of the week, and where necessary the moon phase indicator. The user does not always wish to perform this action, which can be inconvenient, in particular because of its cascade effect in a perpetual calendar mechanism, and in certain cases, he would prefer to adjust the date separately by means of the usual manual correctors, each acting on one of the calendar indicators.