Bhagavad Gita Chapter 8, Verse 17

English Translation

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.

Detailed Commentary

The four Yugas — Satya, Treta, Dvapara, and Kali — together constitute one Chaturyugi. When one thousand Chaturyugis have passed, that constitutes one day of Brahma, and after another thousand Chaturyugis pass, that constitutes one night of Brahma. According to this calculation, Brahma's lifespan is one hundred years. Upon the completion of one hundred years, Brahma becomes absorbed in Paramatma (the Supreme Self); His Brahmaloka also dissolves into Prakriti (primordial matter), and Prakriti in turn merges into Paramatma. No matter how vast an age may be, it too is bound by the limits of time. Even the highest enjoyments, being born of conjunction, become causes of sorrow and are also confined within the boundaries of time. Only Bhagavan (the Lord) is beyond Kala (Time). Thus, one who understands the essence of time does not attach importance to even the divine enjoyments up to Brahmaloka. Connection -- The description of creation (Srishti) and dissolution (Pralaya) related to Brahma's day and night will be presented in the next two verses.