I am taking of the two periods - the dark and the bright. In this connection I want to narrate a story of the Treta age to which I have studied in a book of my respected guru Brahmchari Krishn Dutt Ji. Once in the Treta Yug, when king Raghu was the ruler, it did not rain for a long time. The earth became dry and hot and famine appeared. The king was alarmed. At that time Maharishi Udanga began to collect oblation-materials. He collected the necessary materials for about fifteen days and then performed a grand sacrifice(Yajna) with those materials. As soon as the sacrifice was performed the gods were pleased and rain commenced pouring.
Now it so happened that a mongoose(Maharishi Nevla) which lived in the vicinity arrived there when the sacrifice was over and tried to get itself immersed in the sacrificial remains but the water was not sufficient and only half portion of it became of gold. Then the mongoose began to pass his days in the hope that some another day such sacrifice might be performed and he may get a chance to dip itself in the remains of that sacrifice so that the remaining portion of his body may also become of gold. Days after days went on passing in the hope, and the Dwapar age arrived. In the Dwapar Yug king Yudhishthir performed the Rajsuya Sacrifice.This sacrifice was performed with great splendor. All the royal resources were utilized. The grandeur of the sacrifice was beyond description. The mongoose was also arrived there and dipped itself in the remains of the sacrifice. But the remaining portion of its body did not turn into gold. Then the mongoose became sad. Maharaj Yudhishthir spoke, "O Mongoose why are you sad?" The mongoose replied, "O sir! Once upon a time Mahrishi Udang performed a sacrifice which was not big as of yours but it resulted in bringing rains. I tried to get my body immersed in the remains of that sacrifice, but the remains being not sufficient, only one half of my body could be immersed in it and that half became of gold. O sir! you have performed such a big sacrifice. I was expecting that the remaining half of my body would also turn into gold if I got itself immersed in the remains of this sacrifice and so I did immerse my body, but I am disappointed. The other half of my body could not turn into gold. This is the reason of my sadness. I am unable to understand what sort of sacrifice it is which could not turn the remaining of my body into gold."
On hearing this Yudhishthir was perplexed. Seeing his anxiety the mongoose asked him, "O sir!Why are u getting perplexed?" Yudhishthir replied, "The reason of my perplexity is that I performed such a big sacrifice but it could not turn the remaining half of your body into gold. So it seems that my sacrifice has been worthless." At that time Maharaj Krishna Chandra who was a Yogi having the knowledge of the sixteen kalas said,"O mongoose! Be quiet, darker days are still to come when all sorts of ignorance will pervade the world. Human progress will come to stop. At that time even this half of your body which is of gold will not remain so."
Whatever Lord Krishna said then has come to be true. Some persons say that actions are not required to be done in the present age. Somebody says that he is the incarnation of Krishna and some other body says that he is liberated soul. But all these statements are misleading this world. Krishna used to be delighted with sixteen thousand hymns of Vedas but people say that he had sixteen thousands wives. But he had attained full authority over those hymns and was pleased to ponder over them in a lonely place.
This Yug named Kalyug is the period of ignorance where spiritual light is not well known by persons. A lot of peoples are misguided by others because actual Yoga is not known by them(peoples).
We must think over the teachings of the Vedas today. How these teachings bring about an all round development of man? We must know that human development totally depends upon these teachings. These teachings are divided into two parts - the spiritual and the physical(materialistic). When man is guided by both of them, only then he attains his real development - he achieves his goal of life.
Read this post in Hindi.