Ratekeeper: Watch Accuracy

Every mechanical watch has a rate: a few seconds gained or lost each day, as personal to the movement as a fingerprint. Ratekeeper tells you what yours is, exactly, without a timing machine or a trip to the watchmaker. The method is a five-second pleasure. Set your watch to true time. A day or two later, tap the screen the instant the second hand crosses twelve. Ratekeeper compares that tap to atomic network time (accurate to hundredths of a second) and, from two readings, works out the watch's rate in seconds per day. Gaining or losing, and by exactly how much. That's the whole thing. No microphone, no cradle, no gear. Just your watch, your phone, and a tap. WHAT YOU SEE • The rate, plainly. "+5.4 spd". In words, "gains 5.4 seconds a day," so the sign never has to be decoded. • A history that reads like a story. Every reading is grouped into runs (a run begins each time you set the…