Do you know of any good reference projects to calculate sunrise and sunset times from NTP?

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.