Eternal Calendar Mechanism Explained in Five Minutes

In this video Roy Syvertsen from IWC Schaffhausen explains the Eternal Calendar mechanism in the IWC Portugieser wristwatch.

Thank you to Roy for letting me publish this incredibly succinct explanation! I note that his explanation includes an explanation of how regular year perpetual calendars work. Regular perpetual calendars will need to be manually reset in the year 2100 due to the additional 400 year cycle in the calculation of leap years that they are not designed to account for. By contrast IWC's Eternal Calendar will keep track of leap years until the year 3999 because it includes a mechanism to keep track of the additional 400 year cycle until at least the year 3999 (you just have to keep your watch wound and running for the next 1976 years!). The only reason IWC's Eternal Calendar mechanism can only currently be certified to keep track of leap years to 3999 is because no official decision has been made with respect to leap year accounting for the years 4000 and beyond.

If you're interested, here's a succinct and complete explanation of the leap year rules courtesy of Citizen Watches:
https://www.citizenwatch-global.com/f...

And here's more information about IWC's Portugieser Eternal Calendar wrist watches:
https://www.iwc.com/ch/en/watch-colle...

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