Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 33

Sanskrit:

श्राद्धस्य च विधिं ब्रह्मन् पितृणां सर्गमेव च ।ग्रहनक्षत्रताराणां कालावयवसंस्थितिम् ॥ ३३ ॥

ITRANS:

śrāddhasya ca vidhiṁ brahmanpitṝṇāṁ sargam eva cagraha-nakṣatra-tārāṇāṁkālāvayava-saṁsthitim

Translation:

Please also explain the regulations for offering respects to the forefathers, the creation of the Pitṛloka, the time schedule in the planets, stars and luminaries, and their respective situations.

Purport:

The time durations of day and night as well as months and years are different in the different planets, stars and luminaries. The higher planets like the moon and Venus have time measurements different from those of the earth. It is said that six months of this planet earth equal one day of the higher planets. In Bhagavad-gītā the duration of one day in Brahmaloka is measured to be 1,000 times the four yugas, or 4,300,000 years multiplied by 1,000. And the month and year in Brahmaloka are calculated in that measure.