RayDay: Vitamin D Tracker
Your Daily Sunlight Window
About
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.
What's New in RayDay
1.4.2
October 29, 2026
Bug fixes
Subscriptions & In-App Purchases
RayDay Yearly
A full year of D-Window, IU tracking & forecasts.
Developer apps
FAQ
What is RayDay?
RayDay is a health and fitness app designed to help you understand your daily window for natural Vitamin D production. It calculates optimal sun exposure times based on your location, skin type, and real-time atmospheric data.
How does RayDay calculate the D-Window?
RayDay uses NOAA solar position algorithms to determine when the sun is high enough (above 35° altitude) for UVB rays to penetrate the atmosphere and enable Vitamin D synthesis.
Can RayDay be used worldwide?
Yes, RayDay is designed to work worldwide, accurately calculating your D-Window for any latitude, including polar regions.
Does RayDay offer a free trial?
Yes, RayDay offers a 3-day free trial for its 'RayDay Weekly' subscription plan and a 1-year free trial for the 'Early Supporter Yearly' plan.
What subscription plans are available for RayDay?
RayDay offers 'RayDay Weekly' at $4.99/week, 'Early Supporter Yearly' at $24.99/year, and 'RayDay Yearly' at $24.99/year. Some features require a paid subscription.
What is the age rating for RayDay?
RayDay has an age rating of 4+, making it suitable for a wide range of users.
How often is RayDay updated?
The latest version of RayDay is 1.4.2, and it was last updated on October 29, 2026. This indicates a relatively recent update cycle.
What devices does RayDay support?
RayDay is available for iPhone and iPad devices.
