The contrast between blue and orange/red/pink light wavelengths in morning and evening sunlight is crucial for signaling the body's understanding of time of day.

“The blue-yellow contrast of early day sunlight & the blue-orange contrast of late day sunlight are the optimal stimuli for setting your circadian rhythm, which translates to elevated daytime alertness & focus & quality nighttime sleep.”

“The yellow-blue contrast present at sunrise (& orange-blue at sunset) = the optimal stimulus for setting your circadian rhythm for quality sleep and daytime mood, focus & alertness.”

“Sunrise and sunset = Blue-yellow contrast. (Look for it and compare to mid-day). Blue-yellow opponent neurons in the eye. Circadian rhythm entrainment.”

“Sunrise & sunset = relatively more visible yellow/blue contrast (the optimal stimulus for circadian rhythm setting), yet the brain still “knows” the difference (biologically).”

“At sunrise and sunset, the changing brightness & colors of the sunlight are a big reason why these times are so important to see consistently to reset or strengthen your circadian rhythm.”

“what is so special about that morning and evening sunlight are the contrasts between blues and oranges blues and reds blues and pinks that we can't always see if there's cloud cover but they come through and it's the mathematical difference in their presence a subtraction of a lot of blue and then next to it a lot of orange or a lot of blue and then next to it a lot of pink that triggers the body's understanding that this is morning and evening”

“These melanops and gangling cells have been shown to set the circadian clock and to respond best to the contrast between blue and yellow light of the sort that lands on these cells when you view the sun when it's at so-called low solar angle when it's low in the sky either in the morning or in the evening.”