I’m not sure if it’s because I’ve traveled so much the last few years or if I never left college-mode, but I find I’m most productive if I either:
A) Wake up at 5am and work through the morning
OR
B) Start working at 8pm or 9pm and work until 2am or 3am.
I find midday and early evening to be my most challenging time to concentrate mentally and prefer physical activity at that time.