In an interview with Mashable, Apple’s VP of Technology Kevin Lynch, who is widely regarded as one of the main architects behind the Apple Watch, explained how the wearable device has been designed to maintain extremely accurate time synchronization. Lynch noted that not only is the Apple Watch designed to be “extraordinarily accurate,” but that any two Apple Watches will remain in perfect synchronization, which can be demonstrated by holding them side-by-side and viewing the second hands moving in “perfect unison.” In the interview, Lynch describes the complex processes that Apple uses to maintain such highly accurate synchronization, including “curating” their own network of “Stratum One” Network Time Protocol (NTP) servers synchronized with atomic clocks at the U.S. Naval Observatory via GPS satellites, which then pass time information on to iPhones — those then synchronize time with Bluetooth-connected Apple Watches, incorporating corrections for time delays in communication.
In addition, the Apple Watch incorporates a crystal temperature-control oscillator to compensate for drift and keep the Apple Watch time-accurate regardless of temperature, and in fact Lynch notes that “as a piece of hardware” the Apple Watch is “far more accurate as a timekeeping device than the iPhone,” describing it as four times better, in fact. Lynch also described how Apple actually tests the accuracy of the Apple Watch using high-speed cameras that record the second hand, frame-by-frame, as it moves around, looking for even the smallest hint of latency.