Twitter co-founder Jack Dorsey's new app, called Sun Day, ostensibly helps users track UV exposure and Vitamin D intake.

Named Sun Day, the app tracks UV exposure and vitamin D intake for users at their location. It is currently available via ...

The Sun Day app, just out in beta, will prompt you on how to prep for being out and about. The founder of Twitter, Jack Dorsey, has a bright idea that he's released as a beta app: Sun Day, for ...

Jack Dorsey, co-founder of Twitter, has launched his second app within a week, Sun Day, designed to help users track their vitamin D intake.