Dim your evening light

Lower overall light intensity at night — the lever that actually moves your clock.

Why it works

Bright light in the evening delays the circadian clock and suppresses melatonin, the hormone signaling biological night. The dominant factor is total light intensity and timing, not just screen color — bright overhead lighting after dusk tells the brain it is still daytime and pushes your sleep window later.

How to do it

1. Lower overall light in the last hour or two before bed — fewer, dimmer, warmer lamps.
2. Switch off bright overhead lights in favor of low, warm sources.
3. Keep the bedroom dark for sleep; small light sources can still intrude.

Evidence

Evening light suppressing melatonin and delaying circadian phase is well documented, with brighter light producing larger suppression and delay. A controlled crossover trial found that evening use of a light-emitting eReader suppressed melatonin, delayed circadian timing, and dulled next-morning alertness compared with reading a printed book. (rct)

Total light intensity and timing matter more than screen "blue light" specifically; dimming the room beats only filtering a screen.

Sources

• Gooley et al. (2011), exposure to room light before bedtime suppresses melatonin, J. Clinical Endocrinology & Metabolism
• Gooley JJ, Chamberlain K, Smith KA, Khalsa SBS, Rajaratnam SMW, Van Reen E, Zeitzer JM, Czeisler CA, Lockley SW. Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans. Journal of Clinical Endocrinology & Metabolism. 2011;96(3):E463–E472.
• Chang A-M, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences (PNAS). 2015;112(4):1232–1237.

Common mistake

Focusing on screen filters while leaving bright overhead lights blazing — the room’s overall brightness is the bigger driver.