your suprachiasmatic nucleus hates day mode, esp at the wrong times of the day/night cycle. For me its always 100% dark mode, plus blue blocking filter glasses and app filter, and add red and UV lights to my computer station to add in a little of what my retina is missing but expecting from fake light sources indoors in front of a screen. Circadian biology is a big deal.

There are several factors that impact our biological clocks when it comes to light:

Time of day

Light frequencies present or absent

Intensity

Flicker amount (different bulbs or screens with different quality power sources affect this one even if we don't sense it)

Angle of incidence