Listen now to the ancient reckoning of time as preserved in the venerable tradition. It is said that ninety additional years are regarded as the year of Dhruva, the steadfast celestial. A hundred years, in the divine measure, are to be understood as the span of the gods. According to those learned in the science of calculation, there are three niyutas—vast millions—of human years. Those who truly know declare that a thousand divine years are to be considered in this reckoning. The measure of yugas, or cosmic ages, is established according to this divine calculation. There are four great divisions: Kṛta, Tretā, Dvāpara, and Kali—these are the yugas, the epochs through which the world cycles. Dvāpara and Kali, too, are counted as yugas, each with their own distinct span. For every yuga, there is a period of twilight—called sandhyā—a portion of twilight, and a duration equal to this twilight. These periods proceed in a set manner, measured in thousands and hundreds. Specifically, three hundred and two hundred are the twilights, and their portions are equal in length. In some cases, the twilight is one hundred, and the portion of twilight is likewise equal. Thus, the fourfold divisions—Kṛta, Tretā, Dvāpara, and Kali—are set. Now, let the years of the Kṛta Yuga be declared. The Kṛta Yuga consists of forty thousand years, and likewise, the other yugas each have their own span. The Tretā Yuga endures for eighty thousand years, the Dvāpara Yuga for twenty thousand, and the Kali Yuga for sixty thousand years. When all yugas are calculated together, their measure is six times sixty hundred thousand. The period of twilight for all four yugas is twenty thousand years. When these yugas are joined together—Kṛta, Tretā, Dvāpara, and Kali—this great span is called a Manvantara, the reign of a Manu. In human reckoning, a Manvantara is said to last thirty crores of years. And the period of twilight, with a little more, not less, is twenty thousand years. Thus, the period of a Manvantara, together with the yugas, has now been described. Let us now speak of what remains to be told about the Tretā, Dvāpara, and Kali yugas. These two yugas—Dvāpara and Kali—which come in order, have not yet been fully described. At the beginning of the Tretā Yuga, Manu, the progenitor, and the seven great sages existed. During this time, the union of husband and wife, the Agnihotra fire sacrifice, and the collections of the Rig, Yajur, and Sāma Vedas were established. The dharma, or righteous conduct, was transmitted through tradition, and the characteristics of proper behavior were set forth. Truthfulness, celibacy, study of the scriptures, and austerity were upheld. In the first Tretā Yuga, these virtues were practiced by the seven sages and by Manu himself. Then, the mantras—sacred utterances such as the Taraka and others—became manifest to them. At that time, various perfections appeared among all living beings. The mantras were revealed anew to the sages through inspiration. The seven sages taught these mantras, and Manu proclaimed the ancient dharma. Because of the restriction of human lifespan, these teachings and practices continued into the Dvāpara Yugas. The divine ones, who are without beginning or end, were created in former times by the Self-born. The doctrines of the Veda, though their meaning is one, change in form from yuga to yuga. In this age, the Shudras perform service-sacrifices, while the best among the twice-born perform recitation-sacrifices. All are active in their rites, fruitful in offspring, prosperous, and happy. The Shudras follow the Vaishyas, and there is mutual devotion among them. Thus is the great cycle of time and dharma, as revealed in the ancient scripture.