Clock widget: how does it decides the dark and light color scheme

The clock widget is capable to show world time but some timezones are shown in dark and some in bright coloured clocks. My guess is that if its night time in that timezone it turns dark and when its daytime it turns light however even at 9AM in Canada or 8 AM in Chicago it shows dark.

Any reasons?
It is definitely a daytime/nighttime indicator for that location. I can't tell exactly but it is something like white from 7 AM - 7PM and dark from 7PM - 7 AM
The last person certainly had the right idea. My strong belief is that they base it on the actual projected sunrise/sunset. For example, while I am answering this question EST, London/Paris, +5/+6 hours respectively are both shown as dark clocks and the sun has not risen. I added Mecca temporarily which is +9 and sunrise already happened so the clock is lit. The only reason I noticed initially is that 3 of my clocks are dark, LA/London/Paris, while the 4th, Japan is light.
I am not sure how it works or if it is buggy. Right now, it’s 10:20am in Singapore (after sunrise), but it still shows black background. It is overcast, so it actually is dark but I doubt that this is taken into account ☺️. So my guess is: it should be sunset/sunrise, but it’s buggy.
It’s supposed to be a daytime/nighttime effect but it’s buggy. However, changing the phone’s time from 24hrs to AM/PM fixed that for me. If yours is already set to 12hrs, try changing to 24.
Mine is already on 24-hr time for as long as I can remember, but the clock colors are still wrong. Looks like it's just on random. :(

It's definitely buggy. It's 2300 in NY now and my widget it light there.. wish they would fix it... It's been buggy for ages

I prefer black or white customizable irrespective of daylight time

Clock widget: how does it decides the dark and light color scheme
 
 
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