Kali-yuga, as mentioned before, is the period of hypocrisy & discontent. It is the winter period of a cycle of four periods, namely Satya-yuga, Treta-yuga, Dvapara-yuga, and Kali-yuga. At the end of Kali-yuga, a new Satya-yuga begins and with it a new cycle. A thousand of these cycles, each lasting 4,320,000 years, make up one day of Lord Brahma. Lord Brahma is the firstborn of the universe. A night of Brahma has the same duration. A day and a night of Brahma combined is a kalpa. A year of Brahma consists of 360 kalpas. Lord Brahma lives 100 years. That is, expressed in atomic time, 311 trillion 40 billion years. That is very long, but in the light of eternity it means little.
In Kali-yuga, people in general are only interested in one of the four religious principles, which is "truth". The other three, "mercy", "discipline" and "hygiene" are of little or no importance. That is why there are large slaughterhouses, there is a lot of gambling, there is a lot of extramarital sex and drug use has practically normalized. In addition, in Kali-yuga there is a need for scriptures. In the other three yugas these are not necessary because then people are much more developed and can immediately understand and remember everything through verbal transmission.
External appearances are usually of great importance in Kali-yuga. Hair style often determines the beauty of a person and by wearing certain clothes one easily judges oneself and others as being of little or great importance. Formal positions many times are more important than delivering positive works. Knowledge is easily judged as ignorance. Ignorance, conversely, is easily judged as knowledge.
The twelfth canto of the Srimad Bhagavatam explains Kali-yuga in detail. However, there is great happiness in this dark period; humbly chanting the Hare Krishna maha-mantra leads to enlightenment and complete liberation from the material energy.