IWC / With ProSet®, everything is fully synchronized and controlled via the crown – forward or backward.

Key Highlights

• IWC’s ProSet® system allows the perpetual calendar to be set both forward and backward using a single crown position — no correctors or sequences required.
• The mechanism is rooted in the legendary perpetual calendar architecture designed by Kurt Klaus, with levers replaced by tooth wheels to enable bidirectional adjustment.
• Moon phase accuracy has been improved from one day in 577.5 years to one day in 1,040 years.
• The perpetual calendar is available as Ref. IW339601 in stainless steel on a metal bracelet, and Ref. IW329601 in a white ceramic case on a white rubber strap.
• IWC‘s Gianmarco Nava presented the technical details of this new approach to calendar regulation.

Rethinking the Perpetual Calendar

The perpetual calendar is one of watchmaking’s most revered complications — a mechanism that autonomously tracks the irregularities of the Gregorian calendar, accounting for months of varying length and leap years, without manual date correction. For IWC Schaffhausen, the perpetual calendar has long been a pillar of its haute horlogerie identity, rooted in the work of legendary movement designer Kurt Klaus. What the brand presents now is a fundamental rethinking of how such a complication should interact with the wearer.

The central innovation is ProSet® — a setting system that makes every display on the perpetual calendar fully synchronized and adjustable via the crown, in either direction. This removes one of the most persistent frustrations associated with classical perpetual calendars: the need for dedicated corrector pushers, precise setting sequences, and the anxiety of accidentally advancing a display into an incorrect state. With ProSet®, the entire calendar system moves as one coherent unit, forward or backward, from a single crown position.

For collectors who frequently travel, store multiple watches, or simply value a more considered daily experience, this represents a meaningful departure from convention. The complication remains as demanding to engineer as it ever was — the intelligence has simply been redirected toward ease of use rather than tolerating its own complexity.

The ProSet® Mechanism: From Levers to Tooth Wheels

To understand why ProSet® is technically significant, it helps to appreciate what it replaced. In the original Kurt Klaus perpetual calendar architecture — itself considered a benchmark of the discipline — levers were the key actuating components governing calendar transitions. These levers function effectively in a forward-only setting context but introduce mechanical resistance when any attempt is made to reverse the calendar. IWC’s engineers addressed this by replacing those levers with tooth wheels.

Tooth wheels transmit force bidirectionally with equal mechanical integrity, allowing every calendar display — date, day, month, and year indicator — to move in concert whether advancing or returning. The result is a complex system of gears that faithfully translates the logic of the Gregorian calendar into motion without requiring the wearer to adopt any particular correcting ritual. This is not a simplification of the complication; it is a refinement of its human interface, achieved through a precise mechanical substitution at the heart of the movement.

Moon Phase Precision and Two Material Executions

An Improved Lunar Display

Alongside the bidirectional setting architecture, IWC has substantially improved the moon phase display. The previous calibration offered a deviation of one day in 577.5 years — already an impressive figure by any horological standard. The new generation extends that accuracy to one day in 1,040 years. This improvement reflects the same design philosophy that underpins ProSet® itself: precision in service of long-term reliability, not short-term performance.

Ref. IW339601 and Ref. IW329601

The perpetual calendar is offered in two distinct executions. Ref. IW339601 pairs a stainless steel case with a metal bracelet, lending it a robust, versatile character well suited to collectors who value wearing their most complex pieces daily. Ref. IW329601 takes a more distinctive path, housing the movement in a white ceramic case worn on a white rubber strap — a combination that projects modernity and lightness. Both references carry the same movement and the same ProSet® functionality; the choice is one of aesthetic preference and wrist presence. For GCC collectors who favour bold material choices and appreciate watches that stand apart visually, the white ceramic execution offers a compelling contrast to more conventional metals.

Why It Matters

IWC Schaffhausen‘s ProSet® perpetual calendar reframes a centuries-old complication as something genuinely accessible without diminishing its mechanical depth. For the discerning collectors and enthusiasts who follow Watches and Wonders and track the leading names in precision horology across the GCC, this is the kind of engineering refinement that warrants close attention — not because it changes what a perpetual calendar is, but because it changes what it is to own one.

Stay ahead of the latest releases. Subscribe to our newsletter for editor-curated coverage of luxury timepieces and jewellery across the GCC.