The IWC Perpetual Calendar2:06 pm
Imagine if you were given a challenge to develop a machine that works without any form of electricity and tells the time, day, date, year and phase of the moon accurately for over 500 years. Also, It must remember to account for leap years. Sounds challenging? Not for IWC. The IWC Perpetual Calendar does just that by channelising the power of your wrist into its mind boggling movement. Its an icon of engineering marvel, design and human success.
The perpetual calendar shows not only the lunar cycles but also the seconds, minutes, hours, date, day, month and year in four digits. Mechanically programmed, the calendar takes into account the different length of the months and even the leap years. It needs no adjustment for the next 577 years.
Analogue date displays with hands have a long tradition in IWC watches featuring perpetual calendars. In the case of the Portugieser Perpetual Calendar, for instance, the date, day and month are to be found on three subdials and, thanks to the clear layout, are extremely easy to read.
The classic moon phase display with discs is usually found at “12 o’clock”. The Ingenieur Constant-Force Tourbillon is one exception and displays the double moon at approximately “1o’clock”. The moon phase display used in the Portugieser Grande Complication is astonishingly accurate and deviates by just 0.002 per cent, or 1 day, in 122 years. The Portuguese Perpetual Calendar is even more precise. Larger moon phase wheels with a higher number of teeth reduce the deviation so drastically that a future inheritor of the watch would theoretically need to take it to a watchmaker to have the moon phase display adjusted by only 1 day in 577.5 years.