Sunmaxxing vs Seize Light

Sunmaxxing is the smart sun-safety companion that turns tanning from guesswork into a science. Whether you're chasing a perfect glow, building a vitamin D habit, or just trying not to burn — Sunmaxxing tells you exactly when to be in the sun, how long to stay, and when to come in. WHY SUNMAXXING The sun is the world's best beauty treatment — and also the leading cause of premature aging and skin cancer. Generic weather apps tell you "UV is high" and leave you guessing. Sunmaxxing does the actual math. We combine your skin type (Fitzpatrick I–VI), live UV for your exact location, cloud cover, surface reflection, and your SPF choice into one personalized number: how many minutes you can safely tan before you burn. CORE BENEFITS (REQUIRE SUBSCRIPTION) • LIVE UV INDEX — Real-time UV at your location, updated every 10 minutes, with hourly forecasts so you can plan around the peaks. • YOUR TAN WINDOW — Sunmaxxing detects when the sun angle hits 35° — the dermatological threshold where you actually start to tan. Inside the window: tan. Outside it: save your skin. • PERSONAL BURN TIMER — A countdown built around YOUR skin type and YOUR SPF. Time the front, flip, time the back. No more guessing when you've had enough. • SPF COACHING — Pick your SPF; we recalculate your safe burn time on the fly. Reminders to reapply every 2 hours. • SUN SESSION TIMER — Track every minute in the sun. Watch your vitamin D climb in real time as you tan. • 7-DAY FORECAST — Plan your week with per-day UV peaks, temps, and conditions. Know which days are made for the beach. • TANNING JOURNAL — Daily selfies stitched into a visual tan-progression timeline. Watch your glow build week over week. • SHARE YOUR PROGRESS — One-tap iOS share to send your glow-up to friends. • ACHIEVEMENT BADGES — 20+ milestones across sessions, streaks, and tan progression. Earn every glow-up. • SMART NOTIFICATIONS — A 15-minute heads-up before your Tan Window opens. Never miss the peak. BUILT ON DERMATOLOGY Every burn-time calculation in Sunmaxxing factors: › Your Fitzpatrick skin type (Minimal Erythemal Dose) › Real-time UV index from WeatherKit › Sun altitude (only altitudes ≥ 35° produce a tan) › Cloud cover (quadratic UV attenuation) › Altitude boost (+11% UV per 1,000m elevation) › Surface reflection (snow 80%, sand 15%, grass 3%) › SPF protection factor (real-world square-root model) We follow WHO UV guidelines, AAD SPF recommendations, and Holick's Rule. Peer-reviewed references (Diffey 1991, Fitzpatrick 1988, Holick 1995, WHO INTERSUN, AAD) are listed in the in-app References screen. WHO SUNMAXXING IS FOR • Beach-goers chasing the perfect summer tan • Vitamin D seekers tracking daily exposure • Outdoor athletes managing burn risk • Fair-skinned people trying not to burn at high noon PRIVACY-FIRST Your location, skin type, and tan journal stay on your device. We don't sell your data. We don't track you across apps. START YOUR FIRST TAN WINDOW TODAY Download Sunmaxxing, personalize your skin type and SPF in under 60 seconds, and get your first Tan Window forecast instantly. For informational purposes only. Sunmaxxing does not provide medical advice. Consult a healthcare professional about your sun exposure plan, especially if you have a history of skin cancer or photosensitive conditions. Sunmaxxing requires an active subscription to unlock all features. If you subscribe to Sunmaxxing, payment will be charged to your Apple Account at the confirmation of purchase. Subscription automatically renews unless it is canceled at least 24 hours before the end of the current period. Your account will be charged for renewal within 24 hours prior to the end of the current period. You can manage and cancel your subscriptions by going to your account settings on the App Store after purchase. See https://www.jakubl.com/privacy/ for the Privacy Policy. Sunmaxxing Terms of Use can be found at https://www.jakubl.com/terms/.

Get the right light at the right time. Seize Light reads where you are and the sky above you, computes the sun's real position on your device, and shows your daily light windows — when to get outside, and when to wind down. Most sun apps just show today's UV number. Seize Light shows your two windows: a morning-light window to help set your body clock, and the vitamin-D window — the part of the day the sun is high enough to make vitamin D — plus an evening wind-down that tells you when to dim the lights. Your Apple Watch's Time in Daylight turns it into a passive daily habit, with a transparent Light Score and a streak. YOUR THREE WINDOWS • Morning light — get outside soon after waking to help set your clock; today's target minutes adjust for cloud cover. • Vitamin-D window — opens when the sun is high and UV is strong enough, and closes when it isn't (it tells you why). Keep it short and sub-erythemal. • Evening wind-down — when to dim the lights as part of a wind-down routine. THE LIGHT SCORE A simple, transparent 0–100 score from three parts — morning light, daylight total, and evening protection — fed by your Apple Watch's Time in Daylight. Missing data is never held against you. Build a daylight streak and watch your 90-day trend. EVERY NUMBER IS CITED The solar math, the UV model, and the vitamin-D estimate all trace to published science in an in-app "How this works" screen. HONEST BY DESIGN • UV comes from weather-forecast data (Apple Weather), not a sensor. • Vitamin-D output is an estimate from a model, not a blood test. • Sun safety first: protection is advised at UV 3+, and the rule is always — don't burn. • General wellness and educational use only — not medical advice. Consult a healthcare professional before making health decisions. PRIVATE BY DESIGN • No account. No sign-up. • The solar and vitamin-D math run on your device; only coarse coordinates are sent, for the weather lookup. • Health data is read-only and never leaves your device, except to sync through your own private iCloud — and it is never used for advertising. Weather data provided by Apple Weather. Carpe lucem. Seize the light.