The newly introduced IWC Portugieser Eternal Calendar has been officially recognised by Guinness World Records as the “most precise lunar phase wristwatch”.

With a theoretical deviation of just one day in 45,361,055 years, the Double Moon™ indication of the Portugieser Eternal Calendar beats the previous world record by more than 43 million years.

This is made possible by a new reduction gear train with three intermediate wheels, which reduces the duration of one calendar month as precisely as possible to the duration of one complete lunar cycle.