Analysis of information sources in references of the Wikipedia article "Yuga Cycle" in English language version.
* HINDUISM: Myths of time and eternity: ... Each yuga is preceded by an intermediate "dawn" and "dusk". The Krita yuga lasts 4,000 god-years, with a dawn and dusk of 400 god-years each, or a total of 4,800 god-years; Treta a total of 3,600 god-years; Dvapara 2,400 god-years; and Kali (the current yuga) 1,200 god-years. A mahayuga thus lasts 12,000 god-years ... Since each god-year lasts 360 human years, a mahayuga is 4,320,000 years long in human time. Two thousand mahayugas form one kalpa (eon) [and pralaya], which is itself but one day in the life of Brahma, whose full life lasts 100 years; the present is the midpoint of his life. Each kalpa is followed by an equally long period of abeyance (pralaya), in which the universe is asleep. Seemingly the universe will come to an end at the end of Brahma's life, but Brahmas too are innumerable, and a new universe is reborn with each new Brahma.
* YUGA: each yuga is progressively shorter than the preceding one, corresponding to a decline in the moral and physical state of humanity. Four such yugas (called ... after throws of an Indian game of dice) make up a mahayuga ("great yuga") ... The first yuga (Krita) was an age of perfection, lasting 1,728,000 years. The fourth and most degenerate yuga (Kali) began in 3102 BCE and will last 432,000 years. At the close of the Kali yuga, the world will be destroyed by fire and flood, to be re-created as the cycle resumes. In a partially competing vision of time, Vishnu's 10th and final AVATAR, KALKI, is described as bringing the present cosmic cycle to a close by destroying the evil forces that rule the Kali yuga and ushering in an immediate return to the idyllic Krita yuga.
The following story is told in the Padma Purana (Chapter 14) ... Devendra raised a legal objection to the above injunction of Vishnu as follows: "You, who incarnated yourself as Rama in the twentyseventh yuga of the last Manvantara for the purpose of killing Ravana, killed my son Bali. Therefore I do not wish to procreate Nara as my son." To this objection of Indra, Vishnu assured him that as a penalty for the mistake of killing Bali, he would be a companion of Nara (Arjuna) who would be born as Indra's son.
Twenty-eight times have the Vedas been arranged by the great Rishis in the Vaivaswata Manwantara in the Dwápara age, and consequently eight and twenty Vyásas have passed away; by whom, in their respective periods, the Veda has been divided into four.
Paraphrased: Deva day equals solar year. Deva lifespan (36,000 solar years) equals 100 360-day years, each 12 months. Mahayuga equals 12,000 Deva (divine) years (4,320,000 solar years), and is divided into 10 charnas consisting of four Yugas: Satya Yuga (4 charnas of 1,728,000 solar years), Treta Yuga (3 charnas of 1,296,000 solar years), Dvapara Yuga (2 charnas of 864,000 solar years), and Kali Yuga (1 charna of 432,000 solar years). Manvantara equals 71 Mahayugas (306,720,000 solar years). Kalpa (day of Brahma) equals an Adi Sandhya, 14 Manvantaras, and 14 Sandhya Kalas, where 1st Manvantara preceded by Adi Sandhya and each Manvantara followed by Sandhya Kala, each Sandhya lasting same duration as Satya yuga (1,728,000 solar years), during which the entire earth is submerged in water. Day of Brahma equals 1,000 Mahayugas, the same length for a night of Brahma (Bhagavad-gita 8.17). Brahma lifespan (311.04 trillion solar years) equals 100 360-day years, each 12 months. Parardha is 50 Brahma years and we are in the 2nd half of his life. After 100 years of Brahma, the universe starts with a new Brahma. We are currently in the 28th Kali yuga of the first day of the 51st year of the second Parardha in the reign of the 7th (Vaivasvata) Manu. This is the 51st year of the present Brahma and so about 155 trillion years have elapsed. The current Kali Yuga (Iron Age) began at midnight on 17/18 February 3102 BC in the proleptic Julian calendar.
According to the traditional time-keeping ... Thus in Brahma's calendar the present time may be coded as his 51st year - first month - first day - 7th manvantara - 28th maha-yuga - 4th yuga or kaliyuga.
In the Gaṇeśa Purāṇa, Gaṇapati is described as taking a different incarnation (avatāra) in each of the four cosmic ages (yugas). In the kṛta yuga, Gaṇeśa incarnates as Vināyaka (or Mahotkaṭa), the son of Kāśyapa and Aditi. ... During the treta yuga, Gaṇapati incarnates as Mayūreśvara, the son of Lord Śiva. ... During the dvapara yuga, Gaṇeśa incarnates as Gajānāna, the son of Lord Śiva. ... During the kali yuga, Gaṇapati incarnates as Dhūmraketu (or Śūrpakarṇa).
The Doubt of Vyāsa: According to the Indian tradition, the sage Vyāsa was the compiler of all the Vedas, and the composer of the Mahābhārata and many other works. The [Bhāgavata Purāṇa] repeats this tradition ...
sahasra-yuga-paryantam ahar yad brahmaṇo viduḥ ।
rātriṁ yuga-sahasrāntāṁ te 'ho-rātra-vido janāḥ ॥ 17 ॥
(17) By human calculation, a thousand ages [yuga] taken together form the duration of Brahmā's one day. And such also is the duration of his night.
The Rig-Veda, which we may reasonably consider to have been in its present form before 1000 B.C., has references to the use of dice, and one of its hymns (Book 10, 34) is a charm to cure an inveterate and unsuccessful gambler of the compulsion to gamble that has ruined him. In the Atharva Veda, also, gambling with dice is mentioned (2.3; 4.38; 6.118; 7.52; 7.109). The Aryans of Rig-Vedic times made their dice of the vibhidaka-tree nuts, and we do not know how they used them. Evidently dicing was considered a fitting vice of kings, and in the ritualistic literature of the centuries following the Rig-Veda, say at around 800 B.C., the consecration ceremonies for a king included a game of dice–which the new king must always win–and there was a special officer to take charge of the dice. In the great epic known as the Mahabharata there are two famous instances of kings ruined by gambling.
In the Vayu Purana (70.47–48) [published by Motilal Banarsidass] there is a description of the length of Ravana's life. It explains that when Ravana's merit of penance began to decline, he met Lord Rama, the son of Dasarath, in a battle wherein Ravana and his followers were killed in the 24th Treta-yuga. ... The Matsya Purana (47/240,243–246) is another source that also gives more detail of various avataras and says Bhagawan Rama appeared at the end of the 24th Treta-yuga.
catur-yuga-sahasraṁ tu brahmaṇo dinam ucyate ।
sa kalpo yatra manavaś caturdaśa viśām-pate ॥ 2 ॥
(2) One thousand cycles of four ages [catur-yuga] constitute a single day of Brahmā, known as a kalpa. In that period, O King, fourteen Manus come and go.
sahasra-yuga-paryantam ahar yad brahmaṇo viduḥ ।
rātriṁ yuga-sahasrāntāṁ te 'ho-rātra-vido janāḥ ॥ 17 ॥
(17) By human calculation, a thousand ages [yuga] taken together form the duration of Brahmā's one day. And such also is the duration of his night.
kṛtaṁ tretā dvāparaṁ ca kaliś ceti catur-yugam ।
anena krama-yogena bhuvi prāṇiṣu vartate ॥ 39 ॥
(39) The cycle of four ages [catur-yugam] — Satya, Tretā, Dvāpara, and Kali — continues perpetually among living beings on this earth, repeating the same general sequence of events.
Lord Rāmacandra became King during Tretā-yuga, but because of His good government, the age was like Satya-yuga. Everyone was religious and completely happy.
sahasra-yuga-paryantam ahar yad brahmaṇo viduḥ ।
rātriṁ yuga-sahasrāntāṁ te 'ho-rātra-vido janāḥ ॥ 17 ॥
(17) By human calculation, a thousand ages [yuga] taken together form the duration of Brahmā's one day. And such also is the duration of his night.
The Rig-Veda, which we may reasonably consider to have been in its present form before 1000 B.C., has references to the use of dice, and one of its hymns (Book 10, 34) is a charm to cure an inveterate and unsuccessful gambler of the compulsion to gamble that has ruined him. In the Atharva Veda, also, gambling with dice is mentioned (2.3; 4.38; 6.118; 7.52; 7.109). The Aryans of Rig-Vedic times made their dice of the vibhidaka-tree nuts, and we do not know how they used them. Evidently dicing was considered a fitting vice of kings, and in the ritualistic literature of the centuries following the Rig-Veda, say at around 800 B.C., the consecration ceremonies for a king included a game of dice–which the new king must always win–and there was a special officer to take charge of the dice. In the great epic known as the Mahabharata there are two famous instances of kings ruined by gambling.
