[Zubersoft]

If it wasn't using local time I would think that maybe it's still switching from a night mode to a daytime mode, but I can't really think of anything else off the top of my head that would be related. It would probably be worthwhile to go through all the settings on the device to see if there are any settings that switch things related to text, accessibility, visibility (high-contrast), etc, at certain points of the day.

You'd want to disable things like this: https://support.google.com/chromebook/an...5848?hl=en
https://support.google.com/chromebook/th...mode?hl=en
https://chromeunboxed.com/how-to-set-chr...-schedule/

Mike