RayDay: Vitamin D Tracker

About this app

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. Some features require a paid subscription. DISCLAIMER: RayDay is for educational purposes only. Consult a healthcare professional before changing Vitamin D supplementation or sun exposure habits. --- 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

• Widget now shows the live UV index and solar noon • New vitamin D history charts: track your last 7 and 30 days • Cleaner, decluttered interface • Bug fixes and performance improvements

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1. First observed Aug 31, 2026 · 6:29 PM Free