SUNniDAY

Real-time UV tracking and vitamin D calculator for iOS.

📖 Methodology | 🔒 Privacy Policy

SUNniDAY tells you the current UV index for your location, estimates how much vitamin D your body is synthesising from the sun in real time, and warns you before you burn — personalised to your skin type, clothing, and sunscreen.

Features

• Real-time UV index from your location
• Vitamin D synthesis estimate, minute by minute
• Personal burn-limit countdown
• Skin type, clothing & sunscreen adjustments
• Cloud cover override to fine-tune readings
• Log past sun exposure sessions (with historical UV)
• Vitamin D history chart with a body-store trend line
• Sunrise/sunset and moon phase
• Apple Health integration
• Home screen widget
• No API keys required

Support

Found a bug or have a feature request? Please open an issue — that's the fastest way to reach me.

Requirements

• iOS 17.0+
• iPhone only
• Xcode 15+

Setup

1. Clone the repo
2. Run xcodegen generate to create the Xcode project
3. Open Sunday.xcodeproj
4. Select your development team
5. Build and run

APIs Used

• Open-Meteo for UV data (free, no key)
• Moon phase computed locally on device

Credits

SUNniDAY is based on the open-source Sun Day project by Jack Dorsey, released into the public domain. Huge thanks for the original app and its vitamin D methodology.

License

Released into the public domain under the Unlicense, the same terms as the original project.