Hindu units of time are described in Hindu texts ranging from microseconds to trillions of years, including cycles of cosmic time that repeat general events in Hindu cosmology. Time (kāla) is described as eternal. Various fragments of time are described in the Vedas, Bhagavata Purana, Vishnu Purana, Mahabharata, Surya Siddhanta etc.
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|Unit||Definition||Relation to SI units|
|Truti||त्रुटि||Base unit||≈ 0.30 µs|
|Renu||रेणु||60 Truti||≈ 18 µs|
|Lava||लव||60 Renu||≈ 1080 µs|
|Līkṣaka||लीक्षक||60 Lava||≈ 64.8 ms|
|Lipta||लिप्ता||64.8 Leekshaka||≈ 4.2 s|
|Pala||पल||60 Lipta||≈ 30 s|
|Ghaṭi||घटि||31 Vighaṭi||≈ 1.86 ks|
|Muhūrta||मुहूर्त||2 Ghaṭi||≈ 3.72 ks|
|नक्षत्र अहोरात्रम्||62 Ghaṭī||≈ 86.4 ks|
|32 Muhūrta||≈ 86.4 ks|
|Unit||Definition||Relation to SI units|
|Truti||Base unit||≈ 29.6 µs|
|Tatpara||100 Truti||≈ 2.96 ms|
|Nimesha||30 Tatpara||≈ 88.9 ms|
|Kāṣṭhā||18 Nimesha||≈ 1.6 s|
|Kalā||30 Kāṣṭhā||≈ 48 s|
|Ghatika||30 Kalā||≈ 1.44 ks|
|Muhūrta||2 Ghatika||≈ 2.88 ks|
|30 Muhūrta||≈ 86.4 ks|
Small units of time used in the Vedas:
|Unit||Definition||Relation to SI units|
|Paramāṇu||Base unit||≈ 25 µs|
|Aṇu||2 Paramāṇu||≈ 50 µs|
|Trasareṇu||3 Aṇu||≈ 151 µs|
|Truṭi||3 Trasareṇu||≈ 454 µs|
|Vedha||100 Truṭi||≈ 45 ms|
|Lava||3 Vedha||≈ 0.14 s|
|Nimeṣa||3 Lava||≈ 0.4 s|
|Kṣaṇa||3 Nimesha||≈ 1.22 s|
|Kāṣṭhā||5 Kṣaṇa||≈ 6 s|
|Laghu||15 Kāṣṭhā||≈ 92 s|
|Danda||15 Laghu||≈ 1.38 ks|
|Muhūrta||2 Danda||≈ 2.76 ks|
|Ahorātram||31 Muhūrta||≈ 86.4 ks|
|Masa (month)||30 Ahorātram||≈ 2592 ks|
|Ritu (season)||2 Masa||≈ 5184 ks|
|Ayana||3 Ritu||≈ 15552 ks|
|Samvatsara (year)||2 Ayana||≈ 31104 ks|
|Ahorātram of Deva|
Consists of the following:
Consists of the following:
|Yama||याम||1⁄4 of a day (light) or night||≈ 3 hours|
|Sāvana Ahorātram||सावन अहोरात्रम्||8 Yamas||1 Solar day|
The below table contains calculations of cosmic units of time and the time dilation experienced by different entities, namely Humans, Pitris (forefathers), Devas (gods), Manu (progenitor of humanity), and Brahma (creator god). Calculations use a traditional 360-day year (twelve 30-day months) and a standard 24-hour day for all entities.
|mahā-kalpa||36,000 kalpa & pralaya||311,040,000,000,000 yr||10,368,000,000,000 yr||864,000,000,000 yr||~||100 yr|
|parārdha||1⁄2 mahā-kalpa||155,520,000,000,000 yr||5,184,000,000,000 yr||432,000,000,000 yr||~||50 yr|
|kalpa||14 m + 15 ms; 1,000 cy||4,320,000,000 yr||144,000,000 yr||12,000,000 yr||~||12 hr|
|manvantara [m]||71 catur-yuga||306,720,000 yr||10,224,000 yr||852,000 yr||100 yr|
|manvantara-sandhyā [ms]||Kṛta-yuga length||1,728,000 yr||57,600 yr||4,800 yr||~||17.28 sec|
|catur-yuga [cy]||Kṛta, Tretā, Dvāpara & Kali-yugas||4,320,000 yr||144,000 yr||12,000 yr||~||43.20 sec|
|Kṛta-yuga||sum total||1,728,000 yr||57,600 yr||4,800 yr||~||17.28 sec|
|Kṛta-yuga-sandhyā||1⁄10 Kṛta-yuga[b] length||144,000 yr||4,800 yr||400 yr||~||1.44 sec|
|Kṛta-yuga[b]||4 Kali-yuga[b] lengths||1,440,000 yr||48,000 yr||4,000 yr||~||14.40 sec|
|Tretā-yuga||sum total||1,296,000 yr||43,200 yr||3,600 yr||~||12.96 sec|
|Tretā-yuga-sandhyā||1⁄10 Tretā-yuga[b] length||108,000 yr||3,600 yr||300 yr||~||1.08 sec|
|Tretā-yuga[b]||3 Kali-yuga[b] lengths||1,080,000 yr||36,000 yr||3,000 yr||~||10.80 sec|
|Dvāpara-yuga||sum total||864,000 yr||28,800 yr||2,400 yr||~||8.64 sec|
|Dvāpara-yuga-sandhyā||1⁄10 Dvāpara-yuga[b] length||72,000 yr||2,400 yr||200 yr||~||0.72 sec|
|Dvāpara-yuga[b]||2 Kali-yuga[b] lengths||720,000 yr||24,000 yr||2,000 yr||~||7.20 sec|
|Kali-yuga||sum total||432,000 yr||14,400 yr||1,200 yr||~||4.32 sec|
|Kali-yuga-sandhyā||1⁄10 Kali-yuga[b] length||36,000 yr||1,200 yr||100 yr||~||0.36 sec|
|Kali-yuga[b]||1,000 Deva years||360,000 yr||12,000 yr||1,000 yr||~||3.60 sec|
Time dilation affects the lifespan differently for humans, Pitris (forefathers), Devas (gods), Manus (progenitors of mankind), and Brahma (creator god). The division of a year for each is twelve 30-day months or 360 days, where a day is divided into a 12-hour dawn and 12-hour dusk. A 30-day month amounts to four 7-day weeks with an extra 8th day every two weeks (48-week year). A traditional human year is measured by the sun's northern and southern movements in the sky,[c] where the new year commences only when the sun returns to the same starting point and a pause on the commencement otherwise. For this reason, a traditional 360-day year is equivalent to a modern ≈365.24-day solar or tropical year.
|Brahma year||3,110,400,000,000 yr||103,680,000,000 yr||8,640,000,000 yr||~||1 yr|
|Manu year||3,067,200 yr||102,240 yr||8,520 yr||1 yr|
|Deva year||360 yr||12 yr||1 yr||~|
|Pitri year||30 yr||1 yr||~|
|Human year||1 yr||~|
According to Puranic sources,[d] Krishna's departure marks the end of the human age of Dvapara-yuga and the start of Kali-yuga, which is dated to midnight on 17/18 February 3102 BCE of the proleptic Julian calendar. (See Kali Yuga). We are currently halfway through Brahma's life (maha-kalpa), whose lifespan is equal to the duration of the manifested material elements, from which Brahma manifests his universe in kalpa cycles:
A maha-kalpa is followed by a maha-pralaya (full dissolution) of equal length. Each kalpa (day of Brahma) is followed by a pralaya (night of Brahma or partial dissolution) of equal length. Preceding the first and following each manvantara is a manvantara-sandhya (connection period), each with a length of Krita-yuga (a.k.a. Satya-yuga).
Hindu texts specify that the start and end of each of the yugas are marked by astronomical alignments. This cycle's Treta-yuga began with 5 planets residing in the "Aries" constellation. This cycle's Dvapara-yuga ended with the "Saptarshi" constellation (Ursa major) residing in the "Magha" constellation. The current Kali-yuga will end with the Sun, Moon and Jupiter residing in the "Pushya" sector.[better source needed]
The history of humanity is divided up into four yugas (a.k.a. dharmic ages or world ages)—Kṛta-yuga (pronounced Krita-yuga; a.k.a. Satya-yuga), Tretā-yuga, Dvāpara-yuga and Kali-yuga—each with a 25% decline in dharmic practices and length, giving proportions (caraṇas; pronounced charanas) of 4:3:2:1 (e.g. Satya: 100% start; Kali: 25% start, 0% end), indicating a de-evolution in spiritual consciousness and an evolution in material consciousness. Kali-yuga is followed by Satya-yuga of the next cycle, where a cycle is called a catur-yuga (pronounced chatur-yuga; a.k.a. mahā-yuga). Each yuga is divided into a main period (sometimes called the yuga) and two yuga-sandhis (a.k.a. yuga-sandhyās; connecting periods)—yuga-sandhyā (dawn) and yuga-sandhyāṃśa (a.k.a. yuga-sandhyānśa; dusk)—where each yuga-sandhi lasts for 10% of the main period. Lengths are given in divine years (a.k.a. celestial or Deva years), where a divine year lasts for 360 solar (human) years. A chatur-yuga lasts for 4.32 million solar (12,000 divine) years.[e]
|Krita (Satya)||3,891,102 BCE||1,728,000 (4,800)|
|Treta||2,163,102 BCE||1,296,000 (3,600)|
|Dvapara||867,102 BCE||864,000 (2,400)|
|Kali*||3102 BCE – 428,899 CE[g]||432,000 (1,200)|
|Years: 4,320,000 solar (12,000 divine)|
The lifespan of the Manus (progenitors of mankind) lasts for 100 of their years. Each Manu reigns over a period called a manvantara, each lasting for 71 chatur-yugas. A total of 14 Manus reign successively in one kalpa (day of Brahma). Preceding the first and following each manvantara is a sandhyā (connection period), each lasting the duration of a Satya Yuga. During each manvantara-sandhyā (a.k.a. manvantara-sandhi), Earth (Bhu-loka) is submerged in water.
The lifespan of Brahma (creator god) lasts for 100 of his years. His 12-hour day or kalpa (a.k.a. day of Brahma) is followed by a 12-hour night or pralaya (a.k.a. night of Brahma) of equal length. At the start of his days, he is re-born and creates the planets and the first living entities. At the end of his days, he and his creations are unmanifest (partial dissolution). His 100-year life is called a mahā-kalpa, which is followed by a mahā-pralaya (full dissolution) of equal duration, where the bases of the universe, prakriti, is manifest at the start and unmanifest at the end of a maha-kalpa. His 100-year life is divided into two 50-year periods, each called a parārdha.
Rama appears at the end of Treta-yuga. According to Vayu Purana and Matsya Purana, Rama appeared in the 24th chatur-yuga. According to the Padma Purana, Rama also appeared in the 27th chatur-yuga of the 6th manvantara. 
Krishna's departure marked the end of Dvapara-yuga and the start of Kali-yuga according to Puranic sources.[d] In the 28th chatur-yuga, Krishna appeared as His original self, which only happens once in a kalpa (day of Brahma).
On the very day, and at the very moment the Lord [Krishna] left the earth, on that very day this Kali, the source of irreligiousness, (in this world), entered here.
The Parijata tree proceeded to heaven, and on the same day that Hari [Krishna] departed from the earth the dark-bodied Kali age descended.
It was on the day on which Krishna left the Earth and went to heaven that the Kali age, with time for its body set in.
Each manvantara is preceded and followed by a period of 1,728,000 (= 4K) years when the entire earthly universe (bhu-loka) will submerge under water. The period of this deluge is known as manvantara-sandhya (sandhya meaning, twilight). ... 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.
* 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 ... 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.
catvāri trīṇi dve caikaṁ kṛtādiṣu yathā-kramam ।
saṅkhyātāni sahasrāṇi dvi-guṇāni śatāni ca ॥ 19 ॥
(19) The duration of the Satya millennium equals 4,800 years of the years of the demigods; the duration of the Tretā millennium equals 3,600 years of the demigods; the duration of the Dvāpara millennium equals 2,400 years; and that of the Kali millennium is 1,200 years of the demigods. PURPORT: As aforementioned, one year of the demigods is equal to 360 years of the human beings. The duration of the Satya-yuga is therefore 4,800 × 360, or 1,728,000 years. The duration of the Tretā-yuga is 3,600 × 360, or 1,296,000 years. The duration of the Dvāpara-yuga is 2,400 × 360, or 864,000 years. And the last, the Kali-yuga, is 1,200 × 360, or 432,000 years.
a day in the life of Brahma is divided into 14 periods called manvantaras ("Manu intervals"), each of which lasts for 306,720,000 years. In every second cycle [(new kalpa after pralaya)] the world is recreated, and a new Manu appears to become the father of the next human race. The present age is considered to be the seventh Manu cycle.
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.
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.
In 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.