Tan without burning
Tanny reads the hourly UV index where you actually are and turns it
into a schedule: what time to go out today, how many minutes to stay, and whether
you need sunscreen.
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Live UV indexHourly data for your city, with a plain answer about sunscreen and the SPF you need.
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Your sessionA start time and a duration, recalculated every morning. Tanny avoids the midday peak.
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A timer that keeps runningClose the screen and the countdown continues in the app, on your Lock Screen and in the Dynamic Island.
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Weekly planSessions and rest days, because skin needs recovery time to finish producing melanin.
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Burn protectionHow long unprotected skin has before it reddens, shown at all times.
How the timing is calculated
Tanny does not guess. One UV index unit equals 0.025 W/m² of erythemal
irradiance, and one Standard Erythema Dose equals 100 J/m². From those constants,
plus the minimal erythema dose associated with your skin tone, the app derives how
long a session can last.
Every session is deliberately kept below the threshold where skin reddens. The
dose starts at 55% of that threshold and never exceeds 80%, because skin tone
estimates carry real error and there is no reason to sit near the edge.
Sunscreen guidance follows the WHO Global Solar UV Index recommendations.
UV data comes from Open-Meteo.
Tanny is not a medical device.
It does not diagnose or treat any condition, and all times it shows are estimates.
If your skin reddens, if a mole changes, or if anything feels wrong, get out of the
sun and speak to a doctor. If you have photosensitivity, a history of skin cancer,
or take medication that increases UV sensitivity, talk to a physician before
following any sun exposure schedule.