Comparison

Vitamin D Window Widget vs RayDay

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

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.

Highlights
  • Real-time sun schedule
  • Smart widgets
  • Daily schedule updates
  • Dynamic Island countdown
  • Location-based calculations
  • Offline functionality
  • Solar-themed design
Features
Read full description

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.

About

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.

Highlights
  • D-Window Calculator
  • Live Solar Path animation
  • 7-Day D-Window Forecast
  • Skin Type Personalization
  • Smart Notifications
  • Real-time Atmospheric Data
  • Home Screen Widget
Features
Read full description

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

Vitamin D Window Widget4 screens
RayDay4 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

Vitamin D Window Widget ships an update every 2 weeks, RayDay every 3 weeks. Both last shipped on October 31, 2026.

Scorecard3 real differences · 7 level
Vitamin D Window Widget versus RayDay: the parameters behind the verdict, then further details
ParameterVitamin D Window WidgetRayDay
PriceFreeFree
Rating5.0 (2 ratings) — better3.0 (2 ratings)
Positive reviews100.0% of reviews—
Number of ratings22
Update frequencyEvery 2 weeks — betterEvery 3 weeks
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFreemium
DevicesiPhoneiPhone, iPad — better
Requires iOS18.017.0 — better
Further details — not scored
Size2 MB26 MB
Age rating4+4+
DeveloperAirhopping, SLJakub Laszczyk

Customer experience

Vitamin D Window Widget

All ratings2 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews2 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

RayDay

All ratings2 ratings
Positive50.0%
Neutral0.0%
Negative50.0%

In-app purchases

None

Vitamin D Window Widget

No in-app purchases

3 purchases

RayDay

Subscriptions3
  • RayDay Weekly3 Days trial$4.997 Days
  • RayDay Yearly$24.991 Year
  • Early Supporter Yearly1 Year trial$24.991 Year

Questions

Is Vitamin D Window Widget free?
Vitamin D Window Widget is free to download, with no in-app purchases.
Is RayDay free?
RayDay is free to download, with in-app purchases available.
Which has better reviews, Vitamin D Window Widget or RayDay?
Vitamin D Window Widget is rated higher. Vitamin D Window Widget averages 5.0 out of 5 from 2 ratings, while RayDay averages 3.0 from 2 ratings.
Do Vitamin D Window Widget or RayDay have ads?
Neither Vitamin D Window Widget nor RayDay shows ads.
Which is updated more often, Vitamin D Window Widget or RayDay?
Vitamin D Window Widget ships an update every 2 weeks, and RayDay every 3 weeks. Most recently, Vitamin D Window Widget was updated on October 31, 2026 and RayDay on October 31, 2026.

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