How Kaliyuga Started ?
When Lord Krishna leaves the planet , then Arjuna and other Pandavas became powerless .The whole Yaduvansh was destroyed because of the curse given to Krishna by Gandhari,and none of the Pandavas ,not even Krishna and Balram could save it.
Filled with remorse Pandavas decides to leave for heaven ,making Maharaja Parikshit as the new king of Bharatvarsha. Soon after the Pandavas leaves the earth , Kali,the demon arrives ,who is the personification of evil, jealousy, negativity , illegitimate sexual urges, addictive habits,drinking .
Once when Parikshit was travelling through his kingdom he saw a man who was mercilessly beating a cow and an ox as a club. He was captured by the king and brought to the court. He revealed his identity as Kali and explained about his Adharmic possessions.
The conversation between Maharaja Parikshit and Kali is described in Shreemad Bhagvatam as follows:
SB 1.17.32 – If the personality of Kali, irreligion, is allowed to act as a man-god or an executive head, certainly irreligious principles like greed, falsehood, robbery, incivility, treachery, misfortune, cheating, quarrel and vanity will abound.
SB 1.17.33 – Therefore, O friend of irreligion, (Kali) you do not deserve to remain in a place where experts perform sacrifices according to truth and religious principles for the satisfaction of the Supreme Personality of Godhead.
SB 1.17.34 – In all sacrificial ceremonies, although sometimes a demigod is worshiped, the Supreme Lord Personality of Godhead is worshiped because He is the Supersoul of everyone, and exists both inside and outside like the air. Thus it is He only who awards all welfare to the worshiper.
SB 1.17.35 – Sri Suta Gosvami said: The personality of Kali, thus being ordered by Maharaja Pariksit, began to tremble in fear. Seeing the King before him like Yamaraja, ready to kill him, Kali spoke to the King as follows.
SB 1.17.36 – O Your Majesty, though I may live anywhere and everywhere under your order, I shall but see you with bow and arrows wherever I look.
SB 1.17.37 – Therefore, O chief among the protectors of religion, please fix some place for me where I can live permanently under the protection of your government.
SB 1.17.38 – Suta Gosvami said: Maharaja Pariksit, thus being petitioned by the personality of Kali, gave him permission to reside in places where gambling, drinking, prostitution and animal slaughter were performed.
SB 1.17.39 – The personality of Kali asked for something more, and because of his begging, the King gave him permission to live where there is gold because wherever there is gold there is also falsity, intoxication, lust, envy and enmity.
SB 1.17.40 – Thus the personality of Kali, by the directions of Maharaja Pariksit, the son of Uttara, was allowed to live in those five places.
SB 1.17.41 – Therefore, whoever desires progressive well-being, especially kings, religionists, public leaders, brahmanas and sannyasis, should never come in contact with the four above-mentioned irreligious principles.
Hence Kali got a permanent residence to live in the places where all adharmic and nonsense work are done along with gold.
But Parikshit was a religious king ,during his rule there was negligible sin committed by people. So ,Kali could not prosper in his evil deeds. But it was already decided that Kaliyuga has to begin ,humans have to reach to the extremity of evil deeds .So something has to happen .
As a result a strange incident happened ,which led to death of Maharaja Parikshit.
Once when Parikshit was in the forest for hunting ,he lost the route and entered deep inside the forest . He was so tired and thirsty, so he started searching for water . He saw a sage who was performing his sadhna there. He bowed in front of him and asked for water .But the sage did not replied . Seeing this,Parikshit got angered and he kept a dead snake around the neck of that Brahmin.
Then the Brahmin got into sense and asked the king about this act .The king was deeply regretful and could not understand that how he committed such a sin. Parikshit was an incarnation of Satyayuga and he was filled with all virtuous quality , but to mark the end of Dwapar Yuga and start of Kaliyuga ,his end was necessary .So ,without any control on his senses ,he acted that way. The Brahmin understood everything and forgave the King .
But when Shringi ,the son of Brahman came to know about the incident with his father ,he was filled with anger and cursed Parikshit to die within the next seven days ,and the cause of his death would be a snake bite . As a result of the curse the king died within seven days.
This incident marked the start of Kaliyuga, the yuga of unrighteousness,envy ,jealousy,evil,prostitution, and the end of Dwapar Yuga.
How will Kaliyuga end ?
According to the religious scriptures ,to bring an end to Kaliyuga ,Lord Vishnu will incarnate in the form of Kalki,the warrior and this is going to be the last avatar of Vishnu. The end of Kaliyuga would be the cause for a new beginning where only righteousness ,religious practices and true knowledge would prosper. The supreme lord descends into this material world to perform his pastimes ,to protect his devotees as well as to annihilate the evil and envious.
According to ShreemadBhagvatam :
Athasau yuga sandhyam dasyu prayesu rajasu janita vishnu yasaso namna kalkir jagat patih (S.B 1.3.25)
Thereafter , at the conjuction of two yugas Kali and Satya ,the lord of creation will appear as the Kalki avatar and become the son of Vishnuyasha . At this time the rulers of earth will have degenerated to plunderers.
There are many predictions about the apperance of Lord ,but none of them can be belived to be accurate excepts the fact that we currently live in Kaliyuga( as is understood from the people surrounding us ,their activities ,actions and thinking,including ourselves) and that the supreme lord will surely arrive to annihilate the evils as is stated by Shree krishna in Bhagwadgita :
“यदा यदा हि धर्मस्य ग्लानिर्भवति भारत। अभ्युत्थानमधर्मस्य तदात्मानं सृजाम्यहम्।।”