Overview
DayByDay connects to two health data sources: Apple Health (for iPhone users) and the O2 Ring from Wellue/Viatom (for overnight blood oxygen data). Connecting these means you spend less time logging things manually and more time looking at your progress.
Sync happens automatically
Apple Health syncs automatically every time you open DayByDay. You don't need to tap 'Sync' manually unless you want to pull data right now.
Apple Health (iOS)
Apple Health is the easiest way to get your data into DayByDay. If you have an iPhone — and especially if you have an Apple Watch — connecting it takes about 60 seconds and means you never have to manually log steps, sleep, or workouts.
What data syncs from Apple Health
- ✦Weight — any weight readings logged in Apple Health or by a compatible smart scale
- ✦Steps — daily step count from your iPhone or Apple Watch
- ✦Sleep — sleep stages (awake, REM, core, deep) from Apple Watch
- ✦Workouts — exercise sessions and active calories burned
- ✦Resting heart rate — measured overnight by Apple Watch
How to connect Apple Health
- 1Open DayByDay and go to Settings (bottom of the tab bar).
- 2Tap Health sync.
- 3Tap Connect Apple Health.
- 4A permissions sheet will appear. Toggle on everything you want DayByDay to read.
- 5Tap Allow to confirm. DayByDay will immediately pull your recent data.
You control every permission
You can grant access to some data types and not others. For example, you can allow steps but deny weight if you prefer to log weight manually. Each permission can be changed at any time.
Sync frequency
Apple Health data syncs automatically each time you open DayByDay. In practice, this means your data is always up to date by the time you look at it. You can also trigger an immediate sync by going to Settings → Health sync → Sync now.
What to do if sync stops working
If you are not seeing new data from Apple Health, try these steps in order.
- 1Open your iPhone's Settings app, scroll to Privacy & Security → Health → DayByDay. Make sure the data types you want are toggled on.
- 2Check that Apple Health itself has data. Open the Health app and look at the Browse tab to confirm your data source (Apple Watch, etc.) is writing data there.
- 3Force-quit DayByDay and reopen it. The sync runs on launch, so this often resolves a stuck sync.
- 4Go to Settings → Health sync → Sync now to trigger a manual sync.
- 5If none of the above work, tap Settings → Support → Contact us and let us know what you are seeing.
O2 Ring (Wellue / Viatom)
The O2 Ring is a finger-worn device that tracks your blood oxygen (SpO2) and heart rate continuously throughout the night. It is especially useful if you want detailed overnight oxygen data that goes beyond what Apple Watch provides.
Compatible devices
- ✦Wellue O2Ring
- ✦Viatom O2Ring
- ✦Wellue SleepU
- ✦Any Wellue/Viatom device that exports data via the ViHealth or O2Ring app
What data comes in
- ✦Average SpO2 — your average blood oxygen level overnight
- ✦Lowest SpO2 — the lowest reading recorded during the night
- ✦Oxygen dip rate — the number of oxygen dips per hour (drops of 3% or more)
- ✦O2 Score — DayByDay's composite overnight oxygen quality score
- ✦Overnight heart rate — average heart rate while you slept
How to import O2 Ring data
O2 Ring data does not sync automatically. Wellue and Viatom devices use a proprietary binary format, so you export the file from their companion app and import it into DayByDay manually.
- 1Open the O2Ring app (or ViHealth app) on your phone and sync your device via Bluetooth.
- 2Find the overnight recording you want to import. Tap Share or Export to save the binary data file.
- 3Open DayByDay → Sleep tab and tap the Import button.
- 4Select the file you just exported. DayByDay will parse it and add the data to your sleep history.
O2 Ring and Apple Watch coexist
You can use both sources at the same time. DayByDay keeps the O2 Ring's oxygen data separate from Apple Watch sleep stages, so you get the best of both.
Troubleshooting sync problems
Here are the five most common sync issues and how to fix them.
1. Permissions were revoked
iOS sometimes resets app permissions after an update. Go to Settings app → Privacy & Security → Health → DayByDay and re-enable the data types you want.
2. App was in the background
DayByDay syncs when you open the app. If the app has been running in the background for a long time without being fully opened, data may appear stale. Force-quit and relaunch to trigger a fresh sync.
3. Duplicate entries appearing
DayByDay de-duplicates by date — it keeps one entry per day from Apple Health and never creates duplicates from repeated syncs. If you see duplicates, they likely came from two different sources (e.g., you logged a weight manually and Apple Health also had a reading for that day). You can delete individual entries by swiping left on them.
4. Data is not updating
First, confirm the data exists in the Apple Health app. DayByDay can only read data that is already in Health. If your source device (Apple Watch, smart scale) is not writing to Health, the problem is upstream from DayByDay.
5. Sync shows as 'pending'
A pending sync usually means DayByDay is waiting for an internet connection to upload your data to the cloud. Your data is saved on your device in the meantime. Once you are back online, the sync will complete automatically.
Your health data stays private
Health data synced from Apple Health is processed on your device and stored securely in your personal account. DayByDay never sells your health data and does not share it with third parties for advertising purposes.