SB 5.24.11
yatra ha vava na bhayam aho-ratradibhih kala-vibhagair upalaksyate.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Since there is no sunshine in those subterranean planets, time is not divided into days and nights, and consequently fear produced by time does not exist.