This question was answered the other day. This material world, there are different seasons. They come and go. Just like winter season, spring season, summer season, rainy season, they come and go. Similarly, these yugas by rotation, just like day and night. Now it is night, again the day will come. So day and night is there; it comes by rotation. Similarly these yugas—Satya-yuga, Tretā-yuga, Dvāpara-yuga. So different yugas, just like day means light and night means darkness. Similarly, Satya-yuga means people are all very advanced in spiritual life. Dvāpara-yuga . . . Tretā-yuga means one-fourth sinful, three-fourths pious. Dvāpara-yuga means half and half. Kali-yuga means one-fourth pious and three-fourths sinful. In this way, when Kali-yuga will be finished, again Satya-yuga will come. This is yuga. Is it clear to you? Yes.
So this is not very important thing. This is material changes. They come and go. If we take to Kṛṣṇa consciousness then you are above all these things, because as soon as you become spiritually elevated, these material changes does not effect. Just like Kali-yuga means three-fourths sinful life. So one who has taken to Kṛṣṇa consciousness, becomes devotee, he has no sinful life, although he is in the Kali-yuga. He is not affected. Just like there is police, but if you are not a criminal, the police has nothing to do with you; and if you are a criminal, you may be on the street or in your very nice flat, apartment, the police will be after you and arrest you. So if you become pure, there is no influence of this yuga.