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 watch) and charted so you can watch a rate settle in as a fresh service beds down, or drift as it comes due for one.

• Against a band, if you want one. Hold a watch to −4/+6 seconds a day, or the tighter 0/+5, and see at a glance whether it's keeping to spec.

• By resting position. Dial up, crown down, on the wrist: a mechanical watch runs differently in each. Ratekeeper breaks the rate down position by position and even suggests how to rest it tonight to bring it closer to true.

• A true-time reference clock. A standalone screen showing network time to the tenth of a second, so you can set any watch against it.

BUILT FOR PEOPLE WHO CARE ABOUT WATCHES

• Manual, automatic, quartz, or something else: each is measured on its own terms. • Gentle reminders on your rhythm, so readings land a few days apart the way the math wants. • Export every reading to CSV whenever you like. The data is yours to keep.

PRIVATE BY DEFAULT

No account. No sign-up. No ads. Your watches and readings live on your device and sync across your own devices through your own private iCloud. We can't see them, and nobody is building a profile out of your collection.

Find out how your watches really run. Every one of them has a rate. This is how you learn it.

Have questions? We're here to help. Email us at hello@slowsundaysoftware.com

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