The newly introduced 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.

800 iwc ptg 5057ec moon

The moon phase display is arguably the most charming complication in watchmaking. It displays the current phase of the moon on the dial, ensuring that no full moon is missed – even if it is obscured by clouds. Since the introduction of its perpetual calendar almost four decades ago, IWC Schaffhausen has taken great strides to continuously improve the accuracy of its moon phase displays. 

Developed by IWC Schaffhausen’s former head watchmaker Kurt Klaus, the first perpetual calendar debuted in 1985 with the Da Vinci Perpetual Calendar Chronograph (Ref. IW3750) and offered a moon phase accuracy of 122 years. In 2003, IWC introduced the Portugieser Perpetual Calendar (Ref. 5021), featuring a moon phase display with an enhanced precision of 577.5 years. 

800 iwc iw5057012

The new Portugieser Eternal Calendar pushes the boundaries again, with a theoretical accuracy of more than 45 million years, it has now been officially recognised as the “world’s most precise lunar phase wristwatch” by Guinness World Records (GWR).

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    Established in 1955, GWR has evolved to the globally most recognised authority on record-breaking achievements, verifying and documenting both human and natural records. Before being awarded its title, each record is carefully audited to comply with their strict quality standards and needs to undergo a rigorous verification process.

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