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?
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.
- Difference of Yuga
- Yugadhrama (Peculiar characteristics of Yuga)
- Yuga-Sandhi (the junction of Yugas)
- Yugaamsaka (the part of the Yuga)
- Yugasandhana (joints of two Yugas).
Next Indra says different time systems and conversions. He says
Wise Persons and Sages have said that there are four Yugas in Bharatha subcontinent.They are Krita, Treta, Dvapara and Kali.
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,
- Satya Yuga = 4000 divine (Devas) years
- Treta Yuga = 3000 divine Years
- Dvapara Yuga = 2000 divine years
- Kali Yuga = 1000 divine years
- 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.
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.
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.
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).
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.