How qualities of humans change drastically from Kali Yuga to Satya Yuga?

Question

How People change their behavior to good and virtuous from evil, greedy and lewd within less time at the dawn of Satya Yuga? How can humans who are evil and bad change immediately?

Answer 1

Yugas won't change suddenly. There are transition times between Yugas. Chapter 29 and 31 of ANUSANGA in Brahmanda Purana (Pg- 287-313) describe them in detail. Indra narrates this to sage Suta.

3-4. There are six aspects to be mentioned in regard to set of four Yugas.viz.

1. Yuga
2. Difference of Yuga
3. Yugadhrama (Peculiar characteristics of Yuga)
4. Yuga-Sandhi (the junction of Yugas)
5. Yugaamsaka (the part of the Yuga)
6. Yugasandhana (joints of two Yugas).

Next Indra says different time systems and conversions. He says

23. Wise Persons and Sages have said that there are four Yugas in Bharatha subcontinent.They are Krita, Treta, Dvapara and Kali.

24. The first one is Krita Yuga by name. Thereafter Treta is mentioned.Then Dvapara and Kali. One shall reckon these as Yugas.

(It's strange why they are restricted to India only).

According to this Brahmanda Purana,

Duration

• Satya Yuga = 4000 divine (Devas) years
• Treta Yuga = 3000 divine Years
• Dvapara Yuga = 2000 divine years
• Kali Yuga = 1000 divine years

Yuga Sandhi

• Krita = 400 divine years
• Treta = 300 divine years
• Dvapara = 200 divine years
• Kali = 100 divine years

In all cases Yuga Sandhi = Yugaamsaka.

Sandhyamsa = quarter of (Yuga Sandhi +Yugaamsaka).

1 year of Devas = 360 human years.

Yuga Sankya (total number of total number of divine years in all four yugas) = 12,000 divine years.

So Yuga Sankya = Krita Yuga + Krita's (Yuga Sandhi + Yugaamsaka) + Treta Yuga + Treta Yuga's (Yuga Sandhi + Yugaamsaka) + Dvapara Yuga + Dvapara Yuga's (Yuga Sandhi + Yugaamsaka) + Kali Yuga+ Kali Yuga's (YugaSandhi + Yugaamsaka)

Yuga Sankya = [4000+ (400 + 400)]+ [300 + (300 + 300)] + [2000 + (200+200) ] + [1000 + (100 + 100)]= 4800 + 3600 + 2400 + 1200 = 12,000

So Kali Yuga as total last for 1200 years with 200 divine years (included) as transition time. Those 200 divine years constitute 200*360 = 72,000 years.

Sandhyamsa = 50 divine years (These 50 years are last quarter of 200 years)

Sandhyamsa = 50*360 = 18,000 human years.

These numbers might look big. But what i wanted to convey is there are transition times.

Indra says in Previous Svayambhuva Manvantara,

When Period of Sandhyamsa arrived towards the end of Yugas only a few subjects remained here and there. They were unfortunate fellows with planets adverse to them. Most of them were greedy. They collectively struck and and injured one another. There was anarchy and people killed one another. They adopted a process of Sankara (mixing of castes by means of indiscriminate inter marriage). Only few such people lived.

100. They were oppressed with old age, sickness and hunger. Owing to misery they reached a stage of abject dejection. From this dejected state they reached the state of pondering.Pondering took them to the state of equanimity.

101. Through the state of Equanimity, they had the realization of Atman.Through this knowledge they acquired piety and devotion. Thus those survived the last stage of Kali Yuga acquired tranquility and control of sense.

102. When the close of the Yuga was undergoing transformation,they became quiescent as though they were asleep or inebriated day and night after making mind enchanted (and insensible).

103. Owing to the power of inevitable future, the Krita Yuga set in.When the holy Krita Yuga began to function, the subjects pertaining to Krita Yuga were born of those who survived from the kali Yuga. Those Siddhas who remained then, began to move about invisibly. They established themselves there along with seven sages. The Brahmana, the kshatriyas,the Vaishyas, and the Sudras were those who were remembered as seeds. (They were intended to be the nucleus for the succeeding generations). At that they became identical with those who were born in the closing stages of Kali.They were devoid of any difference.The seven Sages recounted Dharma to them as well as others.

Dharma consists Srauta (as laid in vedas) and Smarta (as laid down in Smirtis). The Sages remain in authority for whole of the Manvantara.

These were how people changed from evil, greedy to virtuous. These changes applies to Kaliyugas of all Mahayugas as said by Sages.

Answer 2

First, at the end of Kali Yuga, this is how humans will behave.

https://www.sacred-texts.com/hin/m03/m03189.htm

And when the end of the Yuga comes, crops will not grow in abundance. And the women will always be sharp in speech and pitiless and fond of weeping. And they will never abide by the commands of their husbands. And when the end of the Yuga comes, sons will slay fathers and mothers. And women, living uncontrolled, will slay their husbands and sons. And, O king, when the end of the Yuga comes, Rahu will swallow the Sun unseasonably. And fires will blaze up on all sides. And travellers unable to obtain food and drink and shelter even when they ask for these, will lie down on the wayside refraining from urging their solicitations. And when the end of the Yuga comes, crows and snakes and vultures and kites and other animals and birds will utter frightful and dissonant cries. And when the end of the Yuga comes, men will cast away and neglect their friends and relatives and attendants. And, O monarch, when the end of the Yuga comes, men abandoning the countries and directions and towns and cities of their occupation, will seek for new ones, one after another. And people will wander over the earth, uttering, 'O father, O son', and such other frightful and rending cries.

What happens after that

And when those terrible times will be over, the creation will begin anew. And men will again be created and distributed into the four orders beginning with Brahmanas. And about that time, in order that men may increase, Providence, according to its pleasure, will once more become propitious. And then when the Sun, the Moon, and Vrihaspati will, with the constellation Pushya , enter the same sign, the Krita age will begin again. And the clouds will commence to shower seasonably, and the stars and stellar conjunctions will become auspicious. And the planets, duly revolving in their orbits, will become exceedingly propitious. And all around, there will be prosperity and abundance and health and peace.

Things Kali Yuga will do before Satya Yuga happens.

And commissioned by Time, a Brahmana of the name of Kalki will take his birth. And he will glorify Vishnu and possess great energy, great intelligence, and great prowess. And he will take his birth in a town of the name of Sambhala in an auspicious Brahmana family. And vehicles and weapons, and warriors and arms, and coats of mail will be at his disposal as soon as he will think of them. And he will be the king of kings, and ever victorious with the strength of virtue. And he will restore order and peace in this world crowded with creatures and contradictory in its course. And that blazing Brahmana of mighty intellect, having appeared, will destroy all things. And he will be the Destroyer of all, and will inaugurate a new Yuga. And surrounded by the Brahmanas, that Brahmana will exterminate all the mlecchas wherever those low and despicable persons may take refuge."

---

He will later conduct a horse sacrifice.

https://www.sacred-texts.com/hin/m03/m03190.htm

"Markandeya continued, 'Having exterminated the thieves and robbers, Kalki will, at a great Horse-sacrifice, duly give away this earth to the Brahmanas, and having established anew the blessed rectitude ordained by the Self-create, Kalki, of sacred deeds and illustrious reputation, will enter a delightful forest, and the people of this earth will imitate his conduct, and when the Brahmanas will have exterminated the thieves and robbers, there will be prosperity everywhere (on earth). And as the countries of the earth will one after another be subjugated, that tiger among Brahmanas, Kalki, having placed deer skins and lances and tridents there, will roam over the earth, adored by foremost Brahmanas and showing his regard for them and engaged all the while in slaughtering thieves and robbers. And he will exterminate the thieves and robbers amid heart-rending cries of 'Oh, father--' 'Oh, mother!--'O son!' and the like, and O Bharata, when sin will thus have been rooted out and virtue will flourish on arrival of the Krita age, men will once more betake themselves to the practice of religious rites.

The main reason there will be a change is because Kali will kill thieves and robbers, he will store peace and balance causing prosperity to be on earth, during satya yuga people will be created again, the sin will be rooted out and virtue will fourish on the arrival of the Krita age, and people will imitate his conduct.