The Xi (ξ) is an automatic worldtimer or GMT movement from Nomos. It was introduced in 2011 and phased out in 2016, replaced by the DUW 5201.

The 2005 introduction of the Alpha movement family was an important turning point for Nomos. Although based on the preceding Nomos 1 TSP, it was largely constructed in-house rather than being a refinished ebauche. This was followed in 2006 by the Nomos Epsilon, the first Nomos movement with automatic winding. Both movements feature a gear train similar to the classic Peseux 7001, but placed in a new enclosure based on the classic Glashütte three-quarter plate design. Nomos updated many of the components, adding hacking seconds, and completely reworked the finishing with rhodium-plated surfaces, blued screws, Glashütte Stripes, and Glashütte solar grinding or Langeleist-Perlage.

The automatic movements consist of Epsilon, Zeta (with date), and Xi (with GMT or world time disc). All three movements measure 13¾ ligne (31 mm) in diameter, but Epsilon is thinnest at 4.3 mm. Like the date wheels on the Nomos Beta, Delta, and Nomos Zeta|Zeta]], the Xi places the world time wheel outisde the periphery of the movement rather than stacked between the bottom plate and the dial. This allows the movement to be thinner than usual.

The world time function consists of an outer disc with city names or airport codes for each timezone and a 24 hour wheel at 3 00 for “home time”. It is operated by means of a pusher located at 2 00 and adjusted with a second pusher at 8 00 set flush with the case. Each time the main pusher is depressed, the central hour hand and location wheel advances by an hour. The second pusher advances the central hour hand separately from the location wheel, allowing it to be “calibrated” for the base timezone.

A direct successor to the Nomos Xi was introduced in 2014, the DUW 5201 featuring the Nomos Swing System. The Xi calibre was phased out and retired in 2016.

This movement is officially named using the Greek letter “ξ”, but Nomos often writes it as “Xi”.

• Nomos Tangomat GMT - A GMT window with airport codes at 9 00
• Nomos Tangomat GMT Plus - A GMT window with simple “+/-” hour indicators at 9 00
• Nomos Zürich Weltzeit - A full city wheel around the periphery of the dial

This movement is part of a family of Nomos movements produced since 2005. The movement is partially made in-house, though the assortment is supplied by a third-party. It was supplanted by the in-house Nomos Swing System family starting in 2014.

• Nomos Alpha Hand winding
• Nomos Beta Hand winding, date
• Nomos Delta Hand winding, date, power reserve indicator
• Nomos Epsilon Automatic
• Nomos Zeta Automatic, date
• Nomos Gamma Hand winding, power reserve indicator
• Nomos Xi Automatic, GMT or world time
• Nomos Alpha.2 Hand winding, 2 hands

• GMT Watches and the Nomos Zurich Weltzeit