I find that advice vague. What does "avoiding the day" even mean?

Anyway, for me it was easier to wake up earlier than try to do focused work after an exhausting day with children. Doing stuff in the middle of the night is a privilege of the childless anyway.

Nah, I have several friends who work in the middle of the night after the kids have gone to sleep. That seems to be the the optimal solution for evening persons with kids.