I’m specifically looking for small microcontroller implementations for a simple clock project. I want to use a good temperature compensated real time clock and/or network time protocol-only (no sunrise/sunset APIs), to calculate local solar noon, sun rise, and sunset times. Then I want to make my own local time where midnight/bedtime is simply 9 hours before sunrise on any given day. I am in special life circumstances where I have no real use for daily coordinated time. This is a little psychology experiment more than anything else. I’m super rusty on the math.
There’s algorithms that can get sun and moon (and really any celestial body’s) relative position to some place on earth. They don’t need internet connections. They just need historical data, a location, and a time. The latter of the two can be gotten from GPS. Something that can process a few thousand floats per second should be enough processing power.