The moon phase complication is a highly precise mechanical feature that displays the current lunar phase by tracking the 29.530589-day lunar cycle. The mechanism operates using a series of precisely calculated gear ratios to achieve exceptional accuracy.

Key specifications include a module engrenages of 1.191, and an advanced gear train ensuring that the star gear moves 10.588° per day, with a total angular movement of 12.19° per day after accounting for further gear reductions. Over the full 29.530589-day lunar cycle, the system completes 360.00088° of rotation, resulting in an impressively low error of just 0.00088° per day. This translates to a deviation of only 1 day per 1120 years, or an incredible 6 seconds per full lunar cycle.