BG 8.17
सहस्रयुगपर्यन्तमहर्यद्ब्रह्मणो विदुः ।
रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः ॥
रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः ॥
sahasra-yuga-paryantam ahar yad brahmaṇo viduḥ
rātriṁ yuga-sahasrāntāṁ te ’ho-rātra-vido janāḥ
rātriṁ yuga-sahasrāntāṁ te ’ho-rātra-vido janāḥ
Word-for-word meanings
te — those; janāḥ — people; viduḥ — who know; yat — that; ahaḥ — a day; brahmaṇaḥ — of Brahmā; paryantam — extends up to; sahasra yuga — one thousand cycles of four yugas; rātrim — [and that his] night; antām — ends; yuga sahasra* — [after] one thousand cycles of four yugas; vidaḥ — are the true knowers; ahaḥ-rātra — [of] day and night.
Translation
Those who know that a day of Brahmā lasts for a thousand cycles of four yugas and that his night also extends for the same span, are the true knowers of day and night.
Notes
* The word yuga here refers to the cycle of four yugas, namely, Satya, Tretā, Dvāpara, and Kali combined together.