CC Madhya 20.390

eka-dui-tina-cāri prahare asta haya
cāri-prahara rātri gele punaḥ sūryodaya
Synonyms: 
eka-dui-tina-cāri — one, two, three, four; prahare — in praharas; asta haya — the sun sets in the evening; cāri-prahara — generally after four praharas; rātri — the night; gele — when it passes; punaḥ — again; sūrya-udaya — the sun rises.
Translation: 
“The day and the night are divided into eight praharas — four belonging to the day and four belonging to the night. After eight praharas, the sun rises again.