Kala — Vedic Units of Time
काल — the measurement of time
From the blink of an eye to the day of Brahma
Kala (काल) means time. Measuring it was the original purpose of Jyotisha: Vedic rituals had to be performed at the right moment of the day, on the right lunar day and in the right season, so the tradition developed an elaborate system of time units. At one end are tiny divisions such as the nimesha, the "twinkling of an eye"; in the middle are practical units like the ghati and muhurta that are still printed in every Panchangam; and at the far end are the cosmological cycles of yugas and kalpas that frame Hindu ideas of history.
Two overlapping scales appear in the texts. The Puranic scale (found for example in the Vishnu Purana) builds upward from the nimesha through the kashtha and kala to the muhurta. The astronomical scale of the Surya Siddhanta builds upward from the prana, the time of one breath, through the pala to the ghati. Both meet at the same day of 30 muhurtas or 60 ghatis, which is why the conversions below work out exactly.
Units within a day
| Unit | Sanskrit | Relation | Modern value | Notes |
|---|---|---|---|---|
| Truti, Paramanu | त्रुटि, परमाणु | Smallest named units | Varies by text | Defined very differently in different Puranas and Siddhanta commentaries; the Surya Siddhanta calls such tiny units "unembodied" (not measurable) time. |
| Nimesha | निमेष | 1/15 kashtha | ≈ 0.21 s | Literally "a twinkling of the eye". |
| Kashtha | काष्ठा | 15 nimeshas | 3.2 s | Puranic scale (e.g. Vishnu Purana). |
| Prana (Asu) | प्राण, असु | 1/6 pala | 4 s | The time of one normal breath; the smallest "real" unit of the Surya Siddhanta. |
| Pala (Vighati, Vinadi) | पल, विघटी | 6 pranas | 24 s | Used in almanacs for precise ending times of tithis and nakshatras. |
| Kala | कला | 30 kashthas | 1.6 min (96 s) | Puranic scale; 30 kalas make a muhurta. |
| Ghati (Ghatika, Nadi, Danda) | घटी, नाडी | 60 palas | 24 min | The working unit of traditional Panchangas; 60 ghatis make one day and night. |
| Muhurta | मुहूर्त | 2 ghatis | 48 min | 30 muhurtas in a day and night; 15 from sunrise to sunset at the equinox. |
| Prahara (Yama) | प्रहर, याम | ¼ of day or night | ≈ 3 h | A "watch"; 4 by day and 4 by night, so its length changes with the season. |
| Ahoratra | अहोरात्र | 60 ghatis, 30 muhurtas | 24 h | One civil day, counted from sunrise to sunrise. |
The ghati and the water clock
The ghati (also ghatika or nadika) takes its name from the ghati-yantra, a water clock made of a small copper bowl with a hole in its base. Floated in a larger vessel, the bowl filled and sank in one ghati, after which an attendant emptied it and restarted it. Because 60 ghatis make a day, a ghati is exactly 24 minutes, and 2.5 ghatis equal one modern hour. Older Panchangas express the end of a tithi or nakshatra as so many ghatis and palas after sunrise; modern ones usually convert these into clock times.
The muhurta
The muhurta of 48 minutes is one of the oldest Indian time units; the Vedanga Jyotisha already uses it, and the Shatapatha Brahmana describes the day and night as having 30 muhurtas. The fifteen muhurtas of the day and the fifteen of the night each have a name and presiding deity. Two of them are widely observed today: the Abhijit Muhurta around local noon and the Brahma Muhurta before sunrise. See our Muhurta guide for the full list.
Seasonal and fixed hours
In everyday use the day (sunrise to sunset) and the night (sunset to sunrise) are divided separately. A prahara is a quarter of the daytime or night-time; Rahu Kalam, Yamagandam and Gulika Kalam are each one eighth of the daytime; and Choghadiya periods are eighths of day and night. These "seasonal hours" stretch and shrink through the year, which is why the clock times of Rahu Kalam change from day to day and city to city.
The calendar: tithi to samvatsara
Above the day, Indian time-reckoning follows the Moon and the Sun together. The tithi is the time the Moon takes to move 12 degrees further from the Sun; because the Moon's speed varies, a tithi can last from about 19 to about 26 hours. Fifteen tithis make a paksha, two pakshas a lunar month, and twelve lunar months a lunar year of about 354 days — eleven days short of the solar year, a gap that is closed by adding an adhika (extra) month roughly every 32 to 33 months. The details are explained on our calendar systems page.
| Unit | Sanskrit | Relation | Duration | Notes |
|---|---|---|---|---|
| Tithi | तिथि | Moon gains 12° on Sun | ≈ 19–26 h (mean ≈ 23.6 h) | The lunar day; its length varies because the Moon's speed varies. |
| Paksha | पक्ष | 15 tithis | ≈ 14.8 days | Shukla (waxing) and Krishna (waning) fortnights. |
| Masa | मास | 30 tithis, 2 pakshas | ≈ 29.53 days | The synodic lunar month (Amanta or Purnimanta); a solar month is the Sun's stay in one rashi. |
| Ritu | ऋतु | 2 months | ≈ 2 months | Six seasons: Vasanta, Grishma, Varsha, Sharad, Hemanta, Shishira. |
| Ayana | अयन | 3 ritus, 6 months | ≈ 6 months | Uttarayana and Dakshinayana, the Sun's northward and southward course. |
| Samvatsara | संवत्सर | 2 ayanas, 12 months | 1 year | Lunar year ≈ 354 days; sidereal solar year ≈ 365.26 days. Named in a 60-year cycle. |
| Kali Yuga | कलियुग | 1 unit | 432,000 years | Began, by the traditional reckoning, in 3102 BCE. |
| Dvapara Yuga | द्वापरयुग | 2 units | 864,000 years | Includes its dawn and dusk (sandhya and sandhyamsha). |
| Treta Yuga | त्रेतायुग | 3 units | 1,296,000 years | |
| Krita (Satya) Yuga | कृतयुग | 4 units | 1,728,000 years | |
| Mahayuga (Chaturyuga) | महायुग | 4 yugas, 10 units | 4,320,000 years | The full cycle of four ages. |
| Manvantara | मन्वन्तर | 71 mahayugas | 306,720,000 years | The age of one Manu; followed by a junction (sandhi) of 1,728,000 years. |
| Kalpa | कल्प | 14 manvantaras + 15 sandhis = 1,000 mahayugas | 4,320,000,000 years | One day of Brahma; his night is of equal length. |
The cosmic cycles: yugas, manvantaras and kalpas
The Puranas and the Siddhantas share a scheme of very long time cycles. Its basic unit is the mahayuga of 4,320,000 years, divided into four ages in the proportion 4 : 3 : 2 : 1 — Krita (Satya), Treta, Dvapara and Kali. Each age includes a dawn and a dusk. Seventy-one mahayugas form a manvantara, the period presided over by one Manu, and fourteen manvantaras together with fifteen connecting periods make a kalpa of exactly 1,000 mahayugas, or 4.32 billion years. A kalpa is one day of the creator Brahma, followed by a night of equal length.
In the traditional reckoning we are now in the Kali Yuga of the 28th mahayuga of the seventh manvantara (that of Vaivasvata Manu) in the Shveta-Varaha Kalpa. The Kali Yuga is said to have begun in 3102 BCE, a date that Aryabhata used as the epoch of his astronomical calculations. This is why the sankalpa recited at the start of many Hindu rituals names the kalpa, manvantara, yuga, samvatsara, ayana, ritu, masa, paksha and tithi — it locates the ritual precisely in this nested structure of time.
For astronomers these large numbers had a practical purpose. The Siddhantas state the number of revolutions each graha makes in a mahayuga or a kalpa as whole numbers; choosing a very long period allowed planetary motions to be expressed in integers, with all planets returning to a common starting point at the beginning of the cycle.
Why it matters today
These units are not merely historical. The daily Panchangam still lists tithis, nakshatras and muhurtas; festivals are fixed by tithi and masa; and ritual timings such as Rahu Kalam are computed as fractions of the actual day. Understanding kala makes it much easier to read an almanac and to see why its timings change with the seasons and from place to place.
Frequently asked questions
How long is one ghati?
One ghati (also called ghatika, nadi or danda) is 24 minutes. Sixty ghatis make a full day and night of 24 hours, and each ghati is divided into 60 palas (vighatis) of 24 seconds each. Traditional Panchangas often give tithi and nakshatra ending times in ghatis and palas counted from sunrise.
How long is a muhurta?
A muhurta is two ghatis, or 48 minutes, so there are 30 muhurtas in a day and night. In practice almanacs divide the actual daytime and night-time each into 15 muhurtas, so a daytime muhurta is a little longer than 48 minutes in summer and shorter in winter.
When did the Kali Yuga begin?
By the reckoning used in Indian astronomy since at least Aryabhata, the Kali Yuga began in 3102 BCE, on 17–18 February by the Julian calendar (reckoned for Ujjain). To convert, roughly 3,101 years are added to the Common Era year to get the number of elapsed Kali years.
How long is a kalpa?
A kalpa, one day of Brahma, lasts 1,000 mahayugas or 4.32 billion years. It contains 14 manvantaras of 71 mahayugas each, plus 15 junction periods (sandhis). Brahma's night is of equal length, so a full day and night of Brahma is 8.64 billion years.
Why does the length of Rahu Kalam or a prahara change through the year?
Many traditional time divisions are fractions of the actual daytime from sunrise to sunset rather than fixed clock lengths. A prahara is a quarter of the daytime, and Rahu Kalam is one eighth of it, so both are longer in summer, when days are long, and shorter in winter.