Morning and afternoon sunlight viewing
Recommends10 min on bright cloudless days, 20 min cloudy, 30-60 min very overcast
His Sleep Toolkit newsletter recommends viewing sunlight in the morning and afternoon, scaling duration to cloud cover, to anchor the sleep-wake rhythm.
“On bright cloudless days: view morning and afternoon sun for 10 min; cloudy days: 20 min; very overcast days 30-60 min.”Andrew Huberman
Source: Toolkit for Sleep (newsletter, 20 Sept 2021)