Bhagavad Gita Chapter 8 Verse 17
भगवद् गीता अध्याय 8 श्लोक 17

सहस्रयुगपर्यन्तमहर्यद्ब्रह्मणो विदुः।
रात्रिं युगसहस्रान्तां तेऽहोरात्रविदो जनाः।।8.17।।



हिंदी अनुवाद - स्वामी तेजोमयानंद
।।8.17।। जो लोग ब्रह्मा जी के एक दिन की अवधि जानते हैं जो कि सहस्र वर्ष की है तथा एक सहस्र वर्ष की अवधि की एक रात्रि को जानते हैं वे दिन और रात्रि को जानने वाले पुरुष हैं।।


Brahma Vaishnava Sampradaya - Commentary

Lord Krishna in order to establish the fact that upon attaining Him there
is no further return to the material existence, He cites the potency of His
unmanifest Brahman by the example of the cyclic dissolution of creation
referring to Brahmas day. The literal meaning for sahasra is one 1000; but
actually it means innumerable for in innumerable creations is dissolution
taking place periodically. The Brahman or the spiritual substratum
pervading all creation is a manifestation of the Supreme Lord and is
supreme as well being the shadow of the universal form. Here Lord Krishna
speaks of dissolution at the end of Brahmas day. Everything comes into
creation by the unmanifest. One Maha Yugas consists of Satya Yuga, Treta
Yuga, Dvarapa Yuga and Kali Yuga equalling 4,320,000 years multiplied by
1000 is 4 billion 320 million years and is a day of Brahma. The same
duration is his night both combined equal 8 billion 640 million years and
which is known as a kalpa.. A year of Brahma is 360 of such kalpas
totalling 26 trillion 438 billion and 400 million years and Brahma lives
for 100 of these years. The Kurma Purana states: For as long as the life of
Brahma is a day for the Supreme Lord and after begins His night. When His
night falls everything gets merged back into Him and when His day dawns
everything emanates out again and creation begins anew. The Supreme Being
who resides in the etheric heart of all beings.

Now begins the summation.

The word sahasra means 1000 but it also indicative of the Brahman or the
spiritual substratum pervading all existence. What is the source of the
Brahman? It is emanating from the Supreme Being. Only the periodic cycles
of night and day are spoken of in reference to the unmanifest Brahman. When
night falls after 4 billion 320 million years everything gets dissolved
back into the unmanifest Brahman. Thus from the statement can be drawn a
conclusion. At the end of day and night of the four-faced Brahma all the
universe is not dissolved, only portions. The Supreme Lord Krishna alone is
eternal. He is transcendental to the constructs of time beyond both the
night and the day. The night and day of Brahmas lifetime are said to be
like the closing and opening of His eyelids