FWIW, until I went in manually, I was monkeying with f.lux around Daylight Savings switches specifically to make it show up the way I wanted it. 4PM is a good time for it to start for me, because it heads off eyestrain at the pass before the sun starts getting low enough and yet my work time's still ongoing. YM, of course, MV.
I can understand wanting the screen to tint reddish when it's 9 or 10 pm, because I should be going to bed soon.
I don't necessarily want it changing colors at 4pm when it starts getting dark here in the winter. At 4:00, I still need to be up for another 6-10 hours.