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 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 Those people who know the day of Brahma which is of a duration of a thousand Yugas (ages) and the night which is also of a thousand Yugas duration, they know day and night. 8.17 Viduh, they know; that ahah, day; brahmanah, of Brahma, of Prajapati, of Virat; yat, which; sahasra-yuga-paryantam, ends in a thousand yugas; and also the ratirm, night; yuga-sahasra-antam, which ends in a thousand yugas, having the same duration as the day. Who knows (these)? In reply the Lord says: Te, they; janah, poeple; ahoratra-vidah, who are the knowers of what day and night are, i.e. the people who know the measurement of time. Since the worlds are thus delimited by time, therefore they are subject to return. What happens during the day and the night of Prajapati is being stated:

।।8.17।। जो मनुष्य ब्रह्माके एक हज़ार चतुर्युगीवाले एक दिनको और सहस्त्र चतुर्युगीपर्यन्त एक रातको जानते हैं, वे मनुष्य ब्रह्माके दिन और रातको जाननेवाले हैं।

।।8.17।। व्याख्या--सहस्रयुगपर्यन्तम् ৷৷. तेऽहोरात्रविदो जनाः --सत्य, त्रेता, द्वापर और कलि--मृत्युलोकके इन चार युगोंको एक चतुर्युगी कहते हैं। ऐसी एक हजार चतुर्युगी बीतनेपर ब्रह्माजीका एक दिन होता है और एक हजार चतुर्युगी बीतनेपर ब्रह्माजीकी एक रात होती है (टिप्पणी प0 470)। दिन-रातकी इसी गणनाके अनुसार सौ वर्षोंकी ब्रह्माजीकी आयु होती है। ब्रह्माजीकी आयुके सौ वर्ष बीतनेपर ब्रह्माजी परमात्मामें लीन हो जाते हैं और उनका ब्रह्मलोक भी प्रकृतिमें लीन हो जाता है तथा प्रकृति परमात्मामें लीन हो जाती है। कितनी ही बड़ी आयु क्यों न हो, वह भी कालकी अवधिवाली ही है। ऊँचे-से-ऊँचे कहे जानेवाले जो भोग हैं, वे भी संयोगजन्य होनेसे दुःखोंके ही कारण हैं--'ये हि संस्पर्शजा भोगा दुःखयोनय एव ते' (गीता 5। 22) और कालकी अवधिवाले हैं। केवल भगवान् ही कालातीत हैं। इस प्रकार कालके तत्त्वको जाननेवाले मनुष्य ब्रह्मलोकतकके दिव्य भोगोंको किञ्चिन्मात्र भी महत्त्व नहीं देते।  सम्बन्ध--ब्रह्माजीके दिन और रातको लेकर जो सर्ग और प्रलय होते हैं, उसका वर्णन अब आगेके दो श्लोकोंमें करते हैं।

By human calculation, a thousand ages taken together form the duration of Brahmā’s one day. And such also is the duration of his night.

The duration of the material universe is limited. It is manifested in cycles of kalpas. A kalpa is a day of Brahmā, and one day of Brahmā consists of a thousand cycles of four yugas, or ages: Satya, Tretā, Dvāpara and Kali. The cycle of Satya is characterized by virtue, wisdom and religion, there being practically no ignorance and vice, and the yuga lasts 1,728,000 years. In the Tretā-yuga vice is introduced, and this yuga lasts 1,296,000 years. In the Dvāpara-yuga there is an even greater decline in virtue and religion, vice increasing, and this yuga lasts 864,000 years. And finally in Kali-yuga (the yuga we have now been experiencing over the past 5,000 years) there is an abundance of strife, ignorance, irreligion and vice, true virtue being practically nonexistent, and this yuga lasts 432,000 years. In Kali-yuga vice increases to such a point that at the termination of the yuga the Supreme Lord Himself appears as the Kalki avatāra, vanquishes the demons, saves His devotees, and commences another Satya-yuga. Then the process is set rolling again. These four yugas, rotating a thousand times, comprise one day of Brahmā, and the same number comprise one night. Brahmā lives one hundred of such “years” and then dies. These “hundred years” by earth calculations total to 311 trillion and 40 billion earth years. By these calculations the life of Brahmā seems fantastic and interminable, but from the viewpoint of eternity it is as brief as a lightning flash. In the Causal Ocean there are innumerable Brahmās rising and disappearing like bubbles in the Atlantic. Brahmā and his creation are all part of the material universe, and therefore they are in constant flux. In the material universe not even Brahmā is free from the process of birth, old age, disease and death. Brahmā, however, is directly engaged in the service of the Supreme Lord in the management of this universe – therefore he at once attains liberation. Elevated sannyāsīs are promoted to Brahmā’s particular planet, Brahmaloka, which is the highest planet in the material universe and which survives all the heavenly planets in the upper strata of the planetary system, but in due course Brahmā and all the inhabitants of Brahmaloka are subject to death, according to the law of material nature.