Vitamin D Window Widget vs RayDay
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Vitamin D Window Widget
This app displays the optimal times of day for natural vitamin D production based on your location and the sun's elevation. It offers real-time sun schedules, smart widgets for home screen access, and notifications to help you maximize your sun exposure.
- Real-time sun schedule
- Smart widgets
- Daily schedule updates
- Dynamic Island countdown
- Location-based calculations
- Offline functionality
- Solar-themed design
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Vitamin D Window shows you the exact hours when sunlight is strong enough for natural vitamin D production at your location. Set up the app and the widget and enjoy the time window in a snapshot. HOW IT WORKS The app calculates solar elevation angles throughout the day using your GPS coordinates. When the sun is high enough above the horizon (above 45° for optimal conditions, above 30° for partial), you get a clear vitamin D time window with start and end times. FEATURES · Real-time sun schedule — sunrise, sunset, and vitamin D hours at a glance · Solar progress bar — see where you are in the day's sun cycle · Smart widgets (small, medium, large) — check your vitamin D window right from your home screen · Daily schedule — it changes depending on the time of the year · Dynamic island with live countdown of the last minutes of vitamin D in the day · Notifications — don't lose the key moments of the day · Location-based — it changes depending on your location · Works offline — no internet connection required after setup · Beautiful solar-themed design — adaptive gradients that follow the sun through the day WIDGETS THAT KEEP YOU INFORMED Add a widget to your home screen and instantly see today's vitamin D window. The small widget features a progress bar in real time as you move through the vitamin D hours. Medium and large widgets show the full sun timeline with sunrise, sunset, and vitamin D periods. After sunset, widgets automatically switch to show tomorrow's schedule — so you always know what's coming. WHO IS THIS FOR? · Health-conscious individuals who want to optimize their sun exposure timing · People living at higher latitudes where vitamin D windows are seasonal (almost all countries) · Outdoor enthusiasts planning activities around peak sun hours · Anyone curious about their local solar schedule PRIVACY FIRST Your location is used only on your device to calculate solar positions. No data is collected, stored on servers, or shared with third parties. Everything runs locally. — Solar calculations powered by the SunCalc algorithm. Vitamin D window times are based on solar elevation angles and may vary depending on individual factors such as skin type, altitude, and atmospheric conditions.
RayDay
This app helps you understand your daily window for natural Vitamin D production. It calculates optimal sun exposure times based on your location and skin type, providing forecasts and real-time atmospheric data.
- D-Window Calculator
- Live Solar Path animation
- 7-Day D-Window Forecast
- Skin Type Personalization
- Smart Notifications
- Real-time Atmospheric Data
- Home Screen Widget
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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
Screenshots
Verdict
The clearest difference is rating: Vitamin D Window Widget at 5.0 against RayDay's 3.0. Vitamin D Window Widget also leads on in-app purchases (none vs 3). On price, ratings volume, update cadence and ads there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. RayDay sells 3 in-app purchases, starting at $4.99 per 7 days. Vitamin D Window Widget asks for nothing beyond the download.
Vitamin D Window Widget holds the better App Store score, 5.0 against 3.0. Both are backed by a comparable volume of ratings — 2 and 2 respectively.
Vitamin D Window Widget ships an update every 2 weeks, RayDay every 3 weeks. Both last shipped on October 31, 2026.
| Parameter | Vitamin D Window Widget | RayDay |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (2 ratings) — better | 3.0 (2 ratings) |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 2 | 2 |
| Update frequency | Every 2 weeks — better | Every 3 weeks |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free — better | Freemium |
| Devices | iPhone | iPhone, iPad — better |
| Requires iOS | 18.0 | 17.0 — better |
| Further details — not scored | ||
| Size | 2 MB | 26 MB |
| Age rating | 4+ | 4+ |
| Developer | Airhopping, SL | Jakub Laszczyk |
Customer experience
Vitamin D Window Widget
RayDay
In-app purchases
Vitamin D Window Widget
No in-app purchases
RayDay
- RayDay Weekly3 Days trial$4.997 Days
- RayDay Yearly$24.991 Year
- Early Supporter Yearly1 Year trial$24.991 Year








