How light exposure calculator Works
The phase-response curve, practically
Light shifts the clock in direction depending on WHEN it arrives: morning light (after your body's temperature minimum) advances the clock; evening light delays it. Jet lag recovery is the deliberate application — seek light in the window that pulls you toward local time, avoid it in the window that pushes you away.
East vs west schedules
Eastward (advance needed): morning light, evening darkness — sunglasses after 8 pm, bright walk at 8 am. Westward (delay needed): evening light, protected mornings — sunglasses before 10 am, sunset walks. Getting the direction backwards makes jet lag worse; this is the one schedule to get right.
Why outdoor beats everything
Outdoor daylight runs 10,000–100,000 lux; indoor office light runs 100–500. The circadian system barely notices indoor light — which is why "I was indoors all day at work" does nothing for the clock, and a 30-minute outdoor walk resets a zone. The schedule is outdoor-walk-centric on purpose.