There’s the perpetual calendar, and now there is the eternal calendar. With a perpetual calendar, the watch automatically adjusts for the leap year which happens once every four years until 2100. The eternal calendar takes it up a notch with a 400-year gear that ensures the date remains accurate until the year 3999!
A little explanation is in order before we go any further: Years in the Gregorian calendar that are divisible by four count as leap years, meaning the a 29th day is added at the end of February. There is, however, an additional correction required to keep the calendar in sync with the actual solar year. Since only those that can be divided by four are leap years, the rest are common years. For instance, 2024 is a leap year while 2100, 2200, and 2300 nare common years.
Watches & Wonders 2024: Highlights from Day 3
IWC Schaffhausen Portugieser Eternal Calendar requires no correction until 3999
The perpetual calendar is calibrated for a four-year cycle, so by design, it will interpret 2100, 2200, and 2300 as a leap year, which they are not. This is why it needs a manual correction three times over 400 years. IWC Schaffhausen resolves this issue with the 400-year gear containing three indentations that cause the calendar to skip three leap years over this period.
This remarkable complication, powered by 52640 calibre that also operates a double perpetual moon phase accurate for up to 45 million years, makes its debut in the new Portugieser in 44.4mm platinum case.
52640 calibre incorporates a 400-year gear
NOW READ
Watches and Wonders 2024: The best Rolex and Patek Philippe watches
Watches and Wonders 2024: How this Van Cleef & Arpels masterpiece blends time, artistry and nature
