Jack Dorsey's New App: Tracking Sun Exposure

Jack Dorsey Launches New App: Sun Day

Jack Dorsey, a co-founder of Twitter, is actively developing and releasing new applications. Following the recent launch of Bitchat, a messaging app utilizing Bluetooth technology, Dorsey has now unveiled Sun Day.

Tracking UV Exposure and Vitamin D

Sun Day is designed to assist users in monitoring their exposure to ultraviolet (UV) radiation and their vitamin D levels. The application is currently accessible through TestFlight for iOS devices.

Furthermore, the source code for Sun Day has been made publicly available on GitHub, allowing developers to clone and examine the application's functionality.

Utilizing Open-Source Coding Tools

Dorsey is participating in the growing trend of "vibe-coding" among developers. However, unlike many who employ tools like Cursor, Claude Code, or Windsurf, he is leveraging an open-source coding platform known as Goose.

How Sun Day Works

The app’s interface is straightforward. It displays the current UV Index for the user’s location, alongside relevant data such as cloud cover, sunrise times, and sunset times.

Users can personalize the app by selecting their skin type from six provided options and specifying the clothing they are wearing.

Based on these inputs, Sun Day calculates the safe duration of sun exposure before potential sunburn occurs.

Vitamin D Intake Monitoring

The application also provides an estimate of the user’s minimum daily vitamin D requirement.

To begin tracking, users initiate a session by pressing the “Track UV exposure” button.

Upon session completion, Sun Day presents the amount of vitamin D accumulated during that session, as well as the total for the day.