One part inside your watch makes one complete rotation every 400 years. Let that sink in. This is the case with the new IWC Portugieser Eternal Calendar ref. IW505701. The calendar will run flawlessly until the year 3999. A regular perpetual calendar would need three corrections (in 2100, 2200, and 2300). Only those centurial years that can be divided by 400 are leap years. The Portugieser Eternal Calendar might not even need a correction in the year 4000 as it has yet to be decided whether that will be a leap year.

IWC Portugieser Eternal Calendar

IWC Portugieser Eternal Calendar IW505701

Also, due to clever engineering and simulation, the Eternal Calendar will only need a correction for its moonphase indicator after 45 million years! The simulation consisted of trying 22 trillion(!) combinations for the wheels that control the moonphase display. The correction is necessary because it doesn’t take precisely a month from one new moon to the next but, rather, 29 days, 12 hours, 44 minutes, and 2.88 seconds. Most higher-end moonphase watches need a correction after 122 years, though some are accurate for up to 577.5 years. A new reduction gear train with three intermediate wheels needed to be developed to get to this amazing result of only one correction after 45 million years. It’s quite an achievement because it also needed to fit within the tiny confines of the movement’s eternal-calendar module.

IWC Portugieser Eternal Calendar

Sapphire dials

All this technology is bundled in a 44.4mm case that is only 15mm thick. On my wrist, it is quite wearable. The box-style crystal shows a lot of the dial and a very thin bezel, giving the watch a sleek look. As you can see in the images that I took, the sub-dials are all sapphire discs. The main dial is also made of sapphire but has gotten a frosted treatment and white lacquer on the underside.

Caliber 52640

All the functions are visible on the dial side, such as a four-digit year indicator, moonphase indicator at 12 o’clock, the date and power reserve at 3 o’clock, the month at 6 o’clock, and the running seconds and day indicator at 9 o’clock. All these complications are powered by IWC’s in-house-developed caliber 52640. This movement offers seven days of power reserve and ticks at 28,800vph (4Hz). Caliber 52640 is visible through the sapphire crystal on the back of the Portugieser Eternal Calendar, which also gives you a view of its 18K rose gold rotor.

IWC manufacture in Schaffhausen

Some thoughts on the new IWC Portugieser Eternal Calendar

The folks at IWC invited us to visit their super modern manufacture in Schaffhausen a little while ago to see the watches under embargo, including this new Portugieser Eternal Calendar. In real life and on the wrist, it’s an incredibly impressive watch. The platinum 44.4mm case by itself is impressive, not to mention the combination of sapphire discs for the time and calendar functions.

IWC’s engineers have solved a nonexistent problem, but it’s a great demonstration of their watchmaking skills in 2024. The regular IWC Portugieser Perpetual Calendar might be a great alternative to those after the same model. The new Portugieser collection is one that you need to see for yourself. And with this Eternal Calendar as the flagship model, it has set the bar very high.

The new IWC Portugieser Eternal Calendar comes on a black leather strap made by Santoni with a platinum folding clasp. The price is at “spot rate”, according to IWC, meaning the base price is CHF150,000 ex. VAT. It will be adjusted to the market of the client.

For more information, visit the IWC website.

Watch specifications

Portugieser Eternal Calendar
Sapphire (white lacquered)
Case Material
Platinum (Pt950)
Case Dimensions
44.4mm (diameter) × 15mm (thickness)
Box-style sapphire
Case Back
Platinum and sapphire crystal
IWC 52640: automatic with manual winding, 28,800vph frequency, 168-hour power reserve, 54 jewels
Water Resistance
5 bar (50 meters)
Black alligator strap by Santoni with platinum folding clasp
Time (hours, minutes, small seconds), eternal calendar (day, date, month, year, moon phases), and power reserve indicator
Spot rate (CHF150,000 ex VAT)