सहस्रयुगपर्यन्तमहर्यद्ब्रह्मणो विदुः । रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः ॥
sahasrayugaparyantamaharyad brahmaṇo viduḥ | rātriṃ yugasahasrāntāṃ te'horātravido janāḥ ||
Translation
Those who know that Brahma's day spans a thousand yugas and that Brahma's night spans a thousand yugas — they are knowers of day and night.
Interpretation
Krishna now describes the scale of cosmic time to put human existence in perspective. A 'day of Brahma' (the cosmic creator) encompasses a thousand yugas (vast cosmic epochs), and so does a 'night of Brahma.' One human yuga (the shortest, Kali Yuga) spans 432,000 human years; a thousand yugas is 4.32 billion years — roughly consistent with modern scientific estimates of Earth's age. The point: what humans consider permanent (civilizations, even the Earth) is part of Brahma's day-cycle, finite on this cosmic scale.