create simple windows 10 program

Is there a way to lock (Win+L) a PC at sunset? I want to be off my PC (windows 10) at sunset and solar noon everyday, locking the PC would be better than having it shutdown since my work is still saved. Locking the PC would make it just enough hassle for me as I would have to log back in so I would get up from my desk. The problem is, sunset and solar noon basically changes everyday, so it would be at different times everyday. I'm open to new ideas as long as it gets me off at sunset and solar noon. It would really improve my life. Thanks