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:
www.citizenwat...
Here's a similar video about Patek Philippe's perpetual calendar (also using a large plexiglass model and also very good): • Patek Phillipe Perpetu...
And here's more information about IWC's Portugieser Eternal Calendar wrist watches in case you want to buy one!
www.iwc.com/ch...
#watchmaking #watchesandwonders2024 #iwcwatches

[@digbethcustard]

Exquisite explanation! Thank you

[@IMakeWatches]

Yeah, thanks to Roy! In addition to knowing how the most complex watch complications work he also speaks six languages! What an amazing mind, right?!

[@VWatchie]

Absolutely marvellous to see. Thank you for sharing! 👍

[@IMakeWatches]

Thanks Vostok! Yes, that was amazing! I'm super glad I videoed it because I had to watch it several times myself to really understand it but now I do!

[@WatchRestorationCottage]

Whoa - I don't fully get it yet, but it's cool to see it modeled at that size. Thanks Dayton.

[@IMakeWatches]

It's all about the Maltese cross gear! Since the 48 tooth wheel takes 4 years (48 months) to do one revolution and the Maltese cross has 5 teeth, the Maltese cross can activate the subsequent 20 tooth 400 year gear one click every 20 years. Therefore it can open that deeper position for the shifting lever at 100, 200, and 300 years, but not 400 (because it is cut deeper for 100, 200, and 300 only.)

[@WatchWithMike]

Whoa, it's so much easier to understand when the model is large! (OK, honestly I don't fully understand, but I feel like I've moved closer to grasping the concept…)

[@IMakeWatches]

Yeah, that model is great! I think Roy's explanation is fantastic it's just that my camera work fails on the necessary close-ups of the golden gear! My aim is to take more time and explain complications thoroughly. This was a great start with an excellent teacher! Thanks for watching, Mike!

[@ElderPinto254]

so nice to see

[@IMakeWatches]

Thanks ElderPinto! Yeah that was really cool! I was glad to see that too!

[@dominickcolasanto6582]

It takes intelligence to make it work. It takes genius to make it work simply.

[@IMakeWatches]

Exactly!

[@kahsings]

Apparently the 1985 module was designed without a computer…

[@IMakeWatches]

That's an interesting comment! Can you be more specific? CAD has gone from 2D drafting to 3D design to 4D simulation over the years and I'm very interested in the historical timeline of that evolution as it pertains to watch movement design.

[@kahsings]

@@IMakeWatches If I recall, the OG creator of this module Mr Kurt Klaus mentioned it in several interviews.

[@IMakeWatches]

@@kahsings Wonderful! Thanks! kzbin.info/www/bejne/hYaqd4qQqp1seLM kzbin.info/www/bejne/launeJ-Xa66lm5Y

[@WatchRestorationCottage]

1 rotation every 400 years.... i'll take their word for it. 😅

[@IMakeWatches]

It's all about the Maltese cross gear! Since the 48 tooth wheel takes 4 years (48 months) to do one revolution and the Maltese cross has 5 teeth, the Maltese cross can activate the subsequent 20 tooth 400 year gear one click every 20 years. Therefore it can open that deeper position for the shifting lever at 100, 200, and 300 years, but not 400 (because it is cut deeper for 100, 200, and 300 only.)

[@WatchRestorationCottage]

@@IMakeWatches i trust you, but I'll need to watch the video again!