Supported Features
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VoiceOver
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Dark Interface
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Reduced Motion
Ratekeeper: Watch Accuracy
Track Daily Rate & Drift
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
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
Terms of Use: https://slowsundaysoftware.com/terms
Privacy Policy: https://slowsundaysoftware.com/privacy
Opened the case, regulated a few stray bugs, closed it back up. Runs a little closer to spec now.
The developer, Slow Sunday Software LLC, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Purchases
- Identifiers
- Usage Data
The developer indicated that this app supports the following accessibility features. Learn More
Information
- Seller
- Slow Sunday Software LLC
- Size
- 6.9 MB
- Category
- Utilities
- Compatibility
Requires iOS 26.5 or later.
- iPhone
Requires iOS 26.5 or later. - iPad
Requires iPadOS 26.5 or later. - Mac
Requires macOS 26.5 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.5 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Unlock the entire app $4.99
- Copyright
- © 2026 Slow Sunday Software LLC