Kali Yuga
Kali Yuga, in Hinduism, is the fourth and worst of the four yugas (world ages) in a Yuga Cycle, preceded by Dvapara Yuga and followed by the next cycle's Krita (Satya) Yuga. It is believed to be the present age, which is full of conflict and sin.According to Puranic sources, Krishna's death marked the end of Dvapara Yuga and the start of Kali Yuga, which is dated to 17/18 February 3102 BCE. Lasting for 432,000 years (1,200 divine years), Kali Yuga began 5,124 years ago and has 426,876 years left as of 2023 CE. Kali Yuga will end in the year 428,899 CE.Near the end of Kali Yuga, when virtues are at their worst, a cataclysm and a re-establishment of dharma occur to usher in the next cycle's Krita (Satya) Yuga, prophesied to occur by Kalki.

Etymology
Yuga (Sanskrit: युग), in this context, means "an age of the world", where its archaic spelling is yug, with other forms of yugam, yugānāṃ, and yuge, derived from yuj (Sanskrit: युज्, lit. 'to join or yoke'), believed derived from *yeug- (Proto-Indo-European: lit. 'to join or unite').Kali Yuga (Sanskrit: कलियुग, romanized: kaliyuga or kali-yuga) means "the age of Kali (demon)", "the age of darkness", "the age of vice and misery", or "the age of quarrel and hypocrisy".A complete description of Kali Yuga is found in the Mahabharata, Manusmriti, Vishnu Smriti, and various Puranas. It is used mathematically in the astronomical texts Aryabhatiya and Surya Siddhanta.

Epigraphy
According to P. V. Kane, one of the earliest inscriptions with one of the four yugas named is the Pikira grant of Pallava Simhavarman (mid-5th century CE):
Who was ever ready to extricate dharma that had become sunk owing to the evil effects of Kaliyuga.
Other epigraphs exist with named yugas in the Old Mysore region of India, published in Epigraphia Carnatica.

Start date
According to the Surya Siddhanta, Kali Yuga began at midnight (00:00) on 18 February 3102 BCE. This is also considered the date on which Krishna left the earth to return to Vaikuntha. This information is placed at the temple of Bhalka, the place of this incident (see photo).
According to the astronomer and mathematician Aryabhata, Kali Yuga started in 3102 BCE. He finished his book Aryabhattiyam in 499 CE, in which he gave the exact year of the beginning of Kali Yuga. He writes that he wrote the book in the "year 3600 of the Kali Age" at the age of 23. As it was the 3600th year of the Kali Age when he was 23 years old, and given that Aryabhata was born in 476 CE, the beginning of the Kali Yuga will come to (3600 - (476 + 23) + 1 (One year from 1 BCE to 1 CE)) = 3102 BCE.According to K. D. Abhyankar, the starting point of Kali Yuga is an extremely rare planetary alignment, which is depicted in the Mohenjo-daro seals. Going by this alignment, the year 3102 BCE is slightly off. The actual date for this alignment is 7 February 3104 BCE. There is also sufficient proof to believe that Vrddha Garga knew of precessions at least by 500 BCE. Garga had calculated the rate of precession to within 30% of what the modern scholars estimate.

Duration and structure
Hindu texts describe four yugas (world ages)⁠ in a Yuga Cycle, where, starting in order from the first age of Krita (Satya) Yuga, each yuga's length decreases by one-fourth (25%), giving proportions of 4:3:2:1. Each yuga is described as having a main period (a.k.a. yuga proper) preceded by its yuga-sandhyā (dawn) and followed by its yuga-sandhyāṃśa (dusk)⁠, where each twilight (dawn/dusk) lasts for one-tenth (10%) of its main period. Lengths are given in divine years (years of the gods), each lasting for 360 solar (human) years.Kali Yuga, the fourth age in a cycle, lasts for 432,000 years (1,200 divine years), where its main period lasts for 360,000 years (1,000 divine years) and its two twilights each lasts for 36,000 years (100 divine years). The current cycle's Kali Yuga, the present age, has the following dates based on it starting in 3102 BCE:
Mahabharata, Book 12 (Shanti Parva), Ch. 231:
(17) A year (of men) is equal to a day and night of the gods ... (19) I shall, in their order, tell you the number of years that are for different purposes calculated differently, in the Krita, the Treta, the Dwapara, and the Kali yugas. (20) Four thousand celestial years is the duration of the first or Krita age. The morning of that cycle consists of four hundred years and its evening is of four hundred years. (21) Regarding the other cycles, the duration of each gradually decreases by a quarter in respect of both the principal period with the minor portion and the conjoining portion itself.
Manusmriti, Ch. 1:
(67) A year is a day and a night of the gods ... (68) But hear now the brief (description of) the duration of a night and a day of Brahman [(Brahma)] and of the several ages (of the world, yuga) according to their order. (69) They declare that the Krita age (consists of) four thousand years (of the gods); the twilight preceding it consists of as many hundreds, and the twilight following it of the same number. (70) In the other three ages with their twilights preceding and following, the thousands and hundreds are diminished by one (in each).
Surya Siddhanta, Ch. 1:
(13) ... twelve months make a year. This is called a day of the gods. (14) ... Six times sixty [360] of them are a year of the gods ... (15) Twelve thousand of these divine years are denominated a Quadruple Age (caturyuga); of ten thousand times four hundred and thirty-two [4,320,000] solar years (16) Is composed that Quadruple Age, with its dawn and twilight. The difference of the Golden and the other Ages, as measured by the difference in the number of the feet of Virtue in each, is as follows : (17) The tenth part of an Age, multiplied successively by four, three, two, and one, gives the length of the Golden and the other Ages, in order : the sixth part of each belongs to its dawn and twilight.

10,000-year sub-period
A dialogue between Krishna and Ganga (goddess) found in the Brahma Vaivarta Purana describes that for the first 10,000 years of Kali Yuga, the ill effects of Kali Yuga will be reduced due to the presence of bhakti yogis and the ability to nullify sinful reactions, after which Earth will be devoid of devout religious people and be shackled by Kali Yuga. Gaudiya Vaishnavism believes this sub-period started later in Kali Yuga with the birth of Chaitanya Mahaprabhu (1486 CE).

Characteristics
Hinduism often symbolically represents morality (dharma) as an Indian bull. In the Satya Yuga, the first stage of development, the bull has four legs, which is reduced by one in each age that follows. By the age of Kali, morality is reduced to only a quarter of that of the golden age, so that the bull of Dharma has only one leg.

References in the Mahabharata
The Kurukshetra War and the decimation of Kauravas thus happened at the Yuga-Sandhi, the point of transition from one yuga to another. The scriptures mention Narada as having momentarily intercepted the demon Kali on his way to the Earth when Duryodhana was about to be born in order to make him an embodiment of arishadvargas and adharma in preparation of the era of decay in values and the consequent havoc.

Prophesied events
A discourse by Markandeya in the Mahabharata identifies some of the attributes of people, animals, nature, and weather during the Kali Yuga.

Other usage
The Kali Yuga is an important concept in both Theosophy and Anthroposophy, and in the writings of Helena Blavatsky, W.Q. Judge, Rudolf Steiner, Savitri Devi, and Traditionalist philosophers such as René Guénon and Julius Evola, among others. Rudolf Steiner believed that the Kali Yuga ended in 1900.

See also
Hindu eschatology
Hindu units of time
Kalpa (day of Brahma)
Manvantara (age of Manu)
Pralaya (period of dissolution)
Yuga Cycle (four yuga ages): Satya (Krita), Treta, Dvapara, and Kali
Historicity of the Mahabharata
Itihasa (Hindu Tradition)
List of numbers in Hindu scriptures
Puranic chronology

Notes
References
Further reading
External links

 The dictionary definition of Kali Yuga at Wiktionary