Protect the evening light-fast to accelerate clock recovery

Dim all light sources aggressively in the two hours before your target bedtime to help the clock arrive where you need it.

Why it works

Social jetlag is partly sustained by evening light exposure that keeps delaying the clock each night. During recovery periods, aggressive evening dimming removes the primary zeitgeber that is fighting the correction. Without the evening light competing against the shifted bedtime, the clock finds the new target faster than with light reduction alone. This is the flip side of morning light anchoring: evening dimming and morning light together create a "circadian squeeze" toward the desired phase.

How to do it

1. Two hours before target sleep, drop all light sources to below 10 lux if possible — candlelight level, warm side-lamps.
2. Put screens into night mode and dim them fully, or wear blue-light-blocking glasses.
3. Keep the bedroom dark for the full night — blackout curtains are worth it if morning light is waking you early.

Evidence

Evening light suppressing melatonin and delaying the clock is well established; the combination of morning light advance and evening light restriction for phase shifting is a clinical approach to social jetlag. (rct)

Total light intensity is more important than light color; the combination of reducing intensity AND shifting to warm light is more effective than either alone.

Sources

• Gooley et al. (2011), exposure to room light before sleep suppresses melatonin, Journal of Clinical Endocrinology & Metabolism

Common mistake

Installing a blue-light filter app while leaving overhead lights at full brightness — the color shift is secondary to the total lux, which the app does nothing about.