रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः।।8.17।।
8.17 Those poeple who are knowers of what day and night are, know the day of Brahma which ends in a thousand yugas [The four yugas (in the human worlds), viz Satya, Treta, Dwapara, and Kali are made up of 4,320,000 years. This period multiplied by a thousand constitutes one day of Brahma. His night also extends over an eal period. See M.S. and V.S.A.], and His night which ends in a thousand yugas.
8.17 These men who know the order of the day and night as established by My will in regard to all beings, beginning with man and ending with Brahma - they understand that what forms Brahmas day is a unit comprising in it a thousand periods of four Yugas (Catur-yugas) and anight is a unit of eal duration.
Sahasrayugaparyantam aharyad brahmano viduh; Raatrim yugasahasraantaam te’horaatravido janaah.
sahasra—one thousand; yuga—age; paryantam—until; ahaḥ—one day; yat—which; brahmaṇaḥ—of Brahma; viduḥ—know; rātrim—night; yuga-sahasra-antām—lasts one thousand yugas; te—they; ahaḥ-rātra-vidaḥ—those who know his day and night; janāḥ—people