RayDay: Vitamin D Tracker
Less Pills, More Sunshine
Free · Designed for iPad. Not verified for macOS.
I built RayDay after years of working indoors left me Vitamin D deficient. The fix wasn't another bottle of pills. It was knowing exactly when the sun was high enough so my body could make Vitamin D the way it always has: naturally, on its own. That's all RayDay does: it tells you your daily sun window, personalized to where you live and your skin type, so you can get Vitamin D the way your body was built to.
FEATURES:
• D-Window Calculator: know exactly when Vitamin D production is possible today and tomorrow
• Live Solar Path: a beautiful animated arc showing the sun's position, sunrise, sunset, and the highlighted D-Window
• 7-Day Forecast: see your D-Window for the coming week
• Skin Type Personalization: your Fitzpatrick type determines how fast you make Vitamin D
• Smart Notifications: get alerted before optimal sun days, plus a heads-up when winter's first D-Window returns
• Atmospheric Data: real-time UV index, cloud cover, humidity, and altitude
• Phase-Aware Design: app colors shift with the time of day. Dawn, daytime, sunset, and night
• Home Screen Widget: a quick glance at your D-Window status
• Works Worldwide: accurate for any latitude, including polar regions
HOW IT WORKS:
RayDay uses NOAA solar position algorithms to calculate the sun's altitude throughout the day. When the sun crosses 35° above the horizon, UVB rays penetrate the atmosphere. That's your D-Window for Vitamin D synthesis.
The app factors in your Fitzpatrick skin type to recommend exposure durations that hit your daily IU goal without overexposure.
DISCLAIMER: RayDay is for educational purposes only. Consult a healthcare professional before changing Vitamin D supplementation or sun exposure habits.
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LEGAL:
Privacy Policy: http://www.jakubl.com/privacy.html
Terms of Use (EULA): http://www.jakubl.com/terms.html
SUPPORT:
support@jakubl.com
X: @jakublaszczyk
Ratings & Reviews
You can now send feedback right from the app. Head to Settings, then Send feedback, to share ideas or report a problem. Plus small fixes and polish under the hood.
The developer, Jakub Laszczyk, 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 Linked to You
The following data may be collected and linked to your identity:
- Contact Info
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Purchases
- User Content
- Usage Data
- Diagnostics
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Jakub Laszczyk
- Size
- 26.4 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
English and 32 more
- English, Arabic, Catalan, Croatian, Czech, Danish, Dutch, Finnish, French, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Malay, Norwegian Bokmål, Polish, Portuguese, Romanian, Russian, Simplified Chinese, Slovak, Spanish, Swedish, Thai, Traditional Chinese, Turkish, Ukrainian, Vietnamese
- Age Rating
4+
- 4+
- Copyright
- © 2026 Jakub Laszczyk