JLC Master Perpetual Calendar Moonphase Issue

Key Points from the Discussion

• The JLC Master Perpetual Calendar's moonphase module, reportedly designed by IWC, is prone to falling out of sync, a recurring issue observed by multiple owners.
• Unlike some other perpetual calendars, the JLC Master Perpetual Calendar typically features a single pusher that advances all calendar indications (month, day, date, year, and moonphase) simultaneously, preventing independent moonphase adjustment.
• To set a moonphase correctly on watches with independent adjustment, one method is to set the date to a known past full moon, then precisely align the moonphase display before advancing the time and date to current.
• A comparison of the JLC moonphase with a known accurate display for December 23, 2021, suggests christianch's JLC showed an 80% waxing moon, while the actual phase was an 80% waning moon, indicating it was off by several days.
• The JLC's moonphase being off by a few days could stem from sloppy initial setting or QC, or it could indicate a problem within the perpetual calendar module itself, especially if the issue developed over time.
• Christianch's experience, coupled with his brother's JLC Master Perpetual Calendar being a full day out of sync and requiring a 1500 CHF repair, raises concerns about the model's reliability and service costs.
• The Glashütte Original's moonphase, in contrast, often allows for independent adjustment via a dedicated pusher, offering greater user control and potentially easier correction.