A light exposure window is a defined block of the day during which you intentionally manage the light at your eyes, either to advance the clock with bright morning light or to protect the evening wind-down by dimming bright and blue-rich sources. It is a behavior schedule, not a single dose.
Why it matters for timing
Light is the strongest input to the circadian system, and the scheduling logic of an evening sleep stack can be distorted by bright overhead light at the wrong time. Treating light as a window puts it on par with the supplement plan rather than as an afterthought.
Morning bright-light window
- Aim for 10 to 30 minutes of outdoor light within the first hour of waking.
- On overcast days, outdoor light usually still carries more signal than standard indoor lighting.
- This window is a low-burden way to support earlier melatonin onset and a steadier morning anchor.
Evening dim-light window
- Begin dimming bright overhead lights about 1 to 2 hours before target sleep.
- Reduce blue-rich screen light at the eyes through distance, dim mode, or filtering.
- Keep the bedroom dark during sleep, with no bright digital clocks pointed at the bed.
Field-level operating notes
Anchor the morning window to wake time and the evening window to target lights-out, then place the rest of the stack against those anchors. Travel and shift work usually require shifting both windows together rather than only one, and the transition days are worth logging as their own context.
Cross-site references
Uncertainty
- Evidence is limited on how much filtered or amber light blocks night-time melatonin suppression.
- Evidence is limited on the minimum daily morning exposure that holds the clock for most users.
How this appears in Unfair
Unfair lets you log a morning and evening light window as context tags so trend reads can separate days where the windows held from days where they drifted.
Clinical safety note
Seasonal affective disorder, retinal disease, and bipolar disorder change how light therapy should be used. Clinician guidance is appropriate before adopting a high-intensity light protocol.