Bright days, dark nights.

Anyone photosensitive, on photosensitising medication, or with an eye condition should ask a clinician first.

• Most trials use light boxes or measured lux, not 'go outside', so the dose you actually get varies with weather, season and latitude.
• The '10–20 minutes' is a practical extrapolation from the phase-response curve's shape, not a measured protocol — the studies measure illuminance and timing, never minutes outside. Overcast days honestly need longer.

Anyone treating a diagnosed condition. Seasonal affective disorder is managed with light-box therapy at specified intensity, duration and timing — a different intervention with its own trial evidence, which none of these papers tests. Do not read this as a substitute for prescribed light therapy, or for treatment of a diagnosed sleep or mood disorder. People with photosensitivity, photosensitising medication, lupus, or a personal or family history of skin cancer should take medical advice on sun exposure before increasing it. Shift workers are explicitly outside this evidence — the wearable light-logger study recruited only people without shift work or jetlag — and daytime light advice can be actively wrong when the work schedule is nocturnal.

• Nobody has trialled this. There is no study — randomised or otherwise — of taking a laptop outside to work. Every paper here tests something adjacent: camping for a week, having a window, self-reported hours outdoors, or wearing a light sensor. The inference from those to 'work outside this afternoon' is ours, not the literature's.
• The camping study moved the clock, not sleep itself. Melatonin timing shifted about two hours earlier, but weekly sleep duration (6.7 versus 6.8 hours) and sleep efficiency (87.6% versus 87.0%) did not change at all, and no mood or wellbeing outcome was measured. Read it as evidence about circadian timing, not as evidence you will sleep more or feel better.