I preety sure that the day times don't matter, the important thing is keeping the 12 of darkness.

I WOULD NOT recomend going dark for 24 hours. Some people use 21:36 hours of light with 12 hours of darkness. That formula will give you 5 daylight times in one week (7days).

You can adjust the daylight all you want; more or less. Just don't break the 12H darkness.