preferences – Always use dark mode, on Mojave

I have chosen Dark mode, under System Preferences > General > Appearance. Yet, it seems whenever starting up the computer, it switches back to Light.

I am guessing there is some “switch theme based on time of day” setting but I can’t find it.

How can I have Dark mode permanently? Is there a workaround at least?

(To be really clear, the options are just Light and Dark, there is no Auto)

Mojave 10.14.2, mid 2014 MacBook Pro