Most of my light bulbs are color-temperature-adjustable. So I wrote a small program which varies the color temperature throughout the day and night.

I started by matching it to the solar elevation, but ultimately I like it more just on a fixed schedule. I've also programmed it to make a more dramatic warm shift near bedtime, and to fade up a bedroom light when it's time to wake up.

Due to the inevitability of scope creep this system also now tracks the charging status and position of my robot vacuum, and I'm working to expand it to collect the 15-minute-interval usage data from my electric provider's website.