Page 18 of Collection Octa by F.P.Journe

the annual calendar is driven by an internally geared large transmission wheel which surrounds the mechanism this activates the main lever every 24 hours the main lever reaches across the movement to advance the date-wheel and its hand day by day the date-wheel in turn drives the month wheel through a rack the days on a regular seven-day cycle are moved forward by the transmission wheel the automatic advance of the date from the end of short months to the beginning of the next month is programmed by a cam mounted on the month-wheel the five recesses around the cam s circumference representing the four months of 30 days and february act on the main lever that advances the date twice at the end of april june september and november the date-hand thus jumps from the 30th to the 1st as it climbs out of the recess for february which is deeper the main lever moves the date three times from february 29 to march 1 it is only at the end of a february with 28 days in three years out of four that the date needs to be advanced manually the date-hand rides up its scale on the curve of a snail cam mounted on the date-wheel on the last day of the month the date lever drops to the bottom of the cam to bring the date-hand flying back to the start of its scale the date-hand itself is mounted on the pinion between two racks one of which incorporates a blade-spring the racks hold the date-hand precisely to the numeral on its scale while controlling its return when the lever falls down the cam.

[close]