Bhagavad-gita As It Is
BG Chapters 1 - 6
Arjuna was truly virtuous, as these qualities, combined with his faith in the words of instruction of Śrī Kṛṣṇa (his spiritual master), indicate.
BG 2.6, Purport: Arjuna did not know whether he should fight and risk unnecessary violence, although fighting is the duty of the kṣatriyas, or whether he should refrain and live by begging. If he did not conquer the enemy, begging would be his only means of subsistence. Nor was there certainty of victory, because either side might emerge victorious. Even if victory awaited them (and their cause was justified), still, if the sons of Dhṛtarāṣṭra died in battle, it would be very difficult to live in their absence. Under the circumstances, that would be another kind of defeat for them. All these considerations by Arjuna definitely proved that not only was he a great devotee of the Lord but he was also highly enlightened and had complete control over his mind and senses. His desire to live by begging, although he was born in the royal household, is another sign of detachment. He was truly virtuous, as these qualities, combined with his faith in the words of instruction of Śrī Kṛṣṇa (his spiritual master), indicate. It is concluded that Arjuna was quite fit for liberation. Unless the senses are controlled, there is no chance of elevation to the platform of knowledge, and without knowledge and devotion there is no chance of liberation. Arjuna was competent in all these attributes, over and above his enormous attributes in his material relationships.
BG Chapters 7 - 12
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.
BG 8.17, Purport: 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.