It's an excellent question. For SN, the best way to take it is supposedly on an empty stomach, so as a practical matter when living with others, I'd probably drink SN a couple hours before I'd normally get out of bed.
Sundown, dusk, twilight and the onset of darkness is poetic, but maybe dawn and sunrise are the most optimistic, for ushering in a better future. (For atheists, a better future could well be nothing, over ongoing pain and suffering.) However, if avoiding discovery is a concern, then darkness is often necessary.