# SUNniDAY — Track UV exposure & vitamin D

> Track UV exposure & vitamin D (iPhone/iPad app by Jesse Wales.)

- Source: https://appshunter.io/ios/app/sunniday/id6787576009 (this page in markdown: same URL + `.md`)
- Developer: [Jesse Wales](https://appshunter.io/developer/6787576011)
- Category: Health & Fitness
- Price: Free
- Age rating: 4+
- Requires: iOS 17.0 · 3 MB
- Languages: American English
- Released: 2026-08-14
- Data updated: 2026-10-31

## What is SUNniDAY?

SUNniDAY tracks real-time UV index and estimates vitamin D production from sun exposure, personalised to your skin type, clothing, and sunscreen.

Know your burn limit before you burn. See how much vitamin D you're synthesising minute by minute. Log past sessions and review your vitamin D history over time.

Features:
• Live UV index from your location
• Vitamin D synthesis calculator
• Skin type, clothing & sunscreen adjustments
• Cloud cover override to fine-tune readings
• Log past sun exposure sessions
• Vitamin D history chart with body-store trend
• Sunrise, sunset and moon phase
• Apple Health integration
• Home screen widget

Based on Sun Day by Jack Dorsey (github.com/jackjackbits/sunday), released into the public domain.

Medical disclaimer: SUNniDAY is for general informational and educational purposes only. It is not a medical device and does not provide medical advice, diagnosis, or treatment. All vitamin D and UV figures are modelled estimates, not measurements. Do not use this app to make medical decisions. Always seek the advice of your physician or other qualified health provider before making decisions about sun exposure, vitamin D supplementation, or any health condition — and use this app only in addition to, not as a substitute for, professional medical advice.

## Is SUNniDAY safe?

Not enough ratings yet to assess SUNniDAY.

## Is SUNniDAY legit?

SUNniDAY has limited verification signals. The AppsHunter Legitimacy Score for SUNniDAY is 58 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 3 releases)

### 1.4 — 2026-09-01

Log Past has been rebuilt.

Past sessions now use the real recorded UV for the day and place you pick, rather than an estimate based on today's weather. Morning readings were also being shown in reverse outside Europe, so a sunny 9am looked like darkness. That is fixed.

The estimate and Save button now always appear. Previously, if the calculation came out at zero the entire panel vanished, leaving no way to save a session. When a period genuinely produced no vitamin D, the app now says why.

### 1.3 — 2026-08-21

Fixes a bug where ending a session without saving it still counted toward your daily dose. If you started a session by accident, this could reduce your absorption rate for the rest of the day.

Cloud cover now adjusts UV using the live forecast instead of a fixed curve, so the rate you see better reflects the sky overhead. Burn time also updates correctly when you change the cloud slider.

Your year of birth has moved into a new Settings screen, reached from the gear in the top left. You can enter it yourself or import it from Apple Health.

Logging a past session no longer affects today's rate, and charts stay readable at larger text sizes.

### 1.2 — 2026-08-14

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-31.*