yāmāḥ - three hours; catvāraḥ - four; catvāraḥ - and four; martyānām - of the human beings; ahanī - duration of day; ubhe - both day and night; pakṣaḥ - fortnight; pañca-daśa - fifteen; ahāni - days; śuklaḥ - white; kṛṣṇaḥ - black; ca - also; mānada - measured.

It is calculated that there are four praharas, which are also called yāmas, in the day and four in the night of the human being. Similarly, fifteen days and nights are a fortnight, and there are two fortnights, white and black, in a month.