Light themes or Dark themes?

Traditionally I've used dark themes for everything I could on all of my devices, as I found it easier on the eyes when I'd usually use my computer (evening - night). Recently, I made the switch back to light stuff as I've been using my computer more for notes and assignments I'd normally hand-write, and I find I get drowsy less and have an easier time using the computer in a bright room than before - I just switched my theme on a whim one morning, so I wasn't expecting that at all!

So now I'm rethinking all my previous bias about dark themes being 'better' regardless of the situation, and I'm curious if anyone here had any thoughts and/or could point me to some reading on the subject (the subject being the effects of light/dark colours in work or concentration). It's something I realize now might be fairly important, as I'm looking at my screen for most of the day, but never really gave much thought before outside of tracking down the 'Dark' theme switch.