Rolex introduced the Chronergy family in 2015 with Cal. 3255, an updated movement for the famous Day-Date (President) model. It is a major redesign, with Rolex claiming that over 90% of the components are redesigned or all-new. The marquee feature for consumers is the “3-day” (70 hour) power reserve, which is made possible by the “Chronergy escapement” with optimized gears and lubricants as well as a longer mainspring inside a thinner barrel. Other notable features include more efficient automatic winding, unrestricted calendar correction, and “backward” (counter-clockwise) time setting.
This movement is described by Rolex as a “Superlative Chronometer.” The company uses this term to indicate their most accurate modern movements. They claim that these are twice as accurate as any official chronometer certification, to -2/+2 seconds per day “after casing.” The Superlative Chronometer test is performed in-house and goes beyond COSC procedures.