SunDay: Vitamin D UV Tracker is a free lifestyle app available on iPhone. Developed by Heuristic Innovations LLC, this app aims to help users monitor their daily vitamin D intake and create healthy habits. With SunDay, users can track their vitamin D intake, measure their progress, and ensure they are safe while being out in the sun.

One of the main features of SunDay is the Solar UV Scanner, which allows users to scan the sun and receive information about sunburn risks. The app also includes a Sun Finder feature for cloudy weather, a Session Timer and Calculator to know when to end a sunbathing session, and a Vitamin D Supplements Calculator for those taking additional supplements.

SunDay also offers daily goals and reminders, profile customization, progress stats and achievements, and even necklace integration for automatic calculations. The app takes into account factors such as skin type, age, weight, and clothing to provide precise calculations.

While SunDay promotes the benefits of sun-generated vitamin D and aims to prevent vitamin D deficiency, it is important to note that the app is intended for educational purposes only and should not be used as a substitute for professional medical advice. Users are advised to consult their healthcare professional before making any health-related decisions based on the app's calculations.