While most tech entrepreneurs pivot from social media to cryptocurrency or AI ventures, Jack Dorsey has taken an unexpectedly analog turn with Sun Day, a mobile application designed to optimize users’ outdoor sun exposure through real-time UV monitoring and vitamin D tracking.
Released in mid-2025, Sun Day represents a curious departure from Silicon Valley’s typical digital obsessions—instead of keeping users glued to screens, it actively encourages them to venture outside (albeit with smartphone in hand, naturally). The application leverages meteorological data and GPS integration to deliver location-specific UV index readings, sunrise and sunset times, and personalized “burn limits” that calculate safe outdoor exposure durations based on individual skin type factors.
A Silicon Valley executive’s surprising pivot toward getting people offline—though paradoxically through yet another smartphone app.
The platform’s core functionality centers on preventive health monitoring, displaying current UV levels alongside daily peak projections while employing algorithmic models to estimate vitamin D synthesis rates. Users receive push notifications when approaching their calculated exposure thresholds—a feature that transforms sun safety from guesswork into data-driven decision making.
Sun Day’s minimalist interface prioritizes quick daily consultations rather than extended engagement, featuring visual UV index scales and exposure timers that integrate seamlessly with established weather services. The application targets outdoor enthusiasts, health-conscious consumers, and professionals whose occupations demand significant sun exposure—from athletes to landscapers to parents monitoring children’s outdoor activities.
What distinguishes this venture from typical wellness applications is its emphasis on balanced exposure rather than complete avoidance. The platform encourages informed outdoor engagement by providing scientific frameworks for understanding UV radiation’s dual nature: its capacity for both harm (sunburns, skin damage) and benefit (vitamin D production, mental health improvements).
The broader implications extend beyond individual health optimization. By democratizing access to professional-grade UV monitoring—previously available only through specialized meteorological equipment—Sun Day potentially reduces sun-related health issues while promoting evidence-based outdoor lifestyle choices. Unlike platforms that generate passive income through user engagement, Sun Day’s design deliberately minimizes screen time in favor of real-world activity. Sun Day follows Dorsey’s recent launch of Bitchat, marking his continued focus on developing diverse applications beyond his Twitter legacy. The app is currently available through TestFlight on Apple’s App Store with limited spots for beta testing.
Whether this represents a genuine paradigm shift toward technology-enabled nature appreciation or simply another layer of digital mediation remains to be determined. Regardless, Dorsey’s latest creation suggests that even former Twitter executives occasionally recognize the value of stepping away from their screens.
