https://nightowl.kramser.xyz/
Donationware

NightOwl will toggle the Dark/Light Modes

TIME BASED
… based on your chosen time. You only have to set it up once, then it will run in the background.
SUN BASED
Want your Mac to be in Dark Mode during night and switched back to Light Mode, when the sun rises? NightOwl does the work for you.
HOTKEYS
It only takes you a second to switch between Mojaves Dark/Light Modes by using the Hotkeys. Press, "Huuhuuhhh", dark. - that easy