Light is the oldest medicine.
SunCycle builds a personal circadian light schedule from your location, the real sun, and peer-reviewed photobiology. No accounts, no tracking, no paid APIs.
Morning light advances your circadian clock — exposure within 1h of waking shifts it earlier by up to 30 min/day.
How it works
Choose your location
Pick a city from our directory, let your browser locate you, or enter coordinates manually. Your data never leaves the browser.
Compute solar events
SunCycle calculates your exact sunrise, sunset, solar noon, twilight, golden hour, and blue hour from real solar geometry (NOAA/Spencer algorithm).
Get your prescription
Receive a four-window light schedule personalized to your chronotype: morning bright light, daylight maintenance, evening dim-down, and blue-light cutoff.
Your personal light planner
Adjust location, date, and chronotype to see your circadian schedule.
Solar timeline
Today's light windows
Light quality
Built on physics, not guesswork
Every recommendation is anchored to peer-reviewed photobiology and real solar geometry.
🌅 Solar noon precision
Sunrise, sunset, twilight, golden hour, and blue hour computed from your exact latitude and longitude using the NOAA solar position model — accurate to ±1 minute.
🔬 Photobiology-backed
Light prescriptions follow CIE S 026:2018 melanopic-EDI standards and research by Brainard (ipRGC sensitivity), Figueiro (morning light), and Zeitzer (evening avoidance).
🦉 Chronotype-aware
Morning lark, dove, or night owl? Your chronotype shifts every window so the schedule matches your biology, not an arbitrary 9-to-5 clock.
🔒 Zero data collection
No accounts, no cookies, no analytics, no third-party APIs. Your location stays in your browser. Share plans via URL if you choose — entirely opt-in.
⚡ Instant deep links
Every plan generates a shareable URL with your coordinates, date, and chronotype. Send it to a friend or bookmark it for later reference.
🌍 37 cities & counting
Pre-loaded directory spanning six continents with valid IANA timezones. Use browser geolocation for anywhere not listed.
Ready to sync with the sun?
Start planning your ideal light day. Free. Forever.