description by ludwig oechslin
task / idea
a date indication integrated within the standard divisions of a 12-hour dial.
solution / implementation
the 12-hour dial is divided into 12 equal sections for the hours and 60 for the minutes per hour or seconds per minute. the date, on the other hand, requires 31 divisions. if, for date purposes, the dial were divided into 30 sections, the 31st of the month would fall on the 1st of the following month. dividing the dial into 30 sections would allow mathematical synergies to be exploited with the 60 minute indices (one day marker every two minutes) and the 10-minute indices (which would act as 5-day markers for the date indication). in the case of months with 31 days, you would need the date indication to remain one extra day on the 31st / 1st – or you would need to get the watch to reverse by one day. to differentiate between the 31st and the 1st, you would need to double the display at the position they share. given that we have a display consisting of a dot travelling under a circle of perforations, there would have to be an additional dot and an additional perforation above or below the 1st of the month to indicate the 31st. if you now incorporate this additional perforation (located above or below the 1st) into the existing circle of perforations, you end up with a spiral moving from the 1st to the 31st of the month. imagine the date dot is in the 31st perforation, and imagine where the date dot would have to be at this moment for the following 1st perforation, you soon see that it would have to be above or below the 30th. if you now join together the date dot for the 1st with the date dot for the 31st, what you end up with under the perforated dial is a curved dash. this curved dash, printed on a disk rotating beneath, and visible through, the date perforations of the dial, replaces the conventional alphanumeric date indication. the date can now, like the time, be told intuitively, and the mechanics driving the function are far simpler than those driving a conventional alphanumeric display. my solution is visually far less intrusive than a conventional alphanumeric display: the date is subordinate to the time, but it remains perfectly readable.