The 11th chapter of the 3rd canto of Srimad Bhagavatam gives us a condensed explanation of the measurement of time according to the Vedas. This gives us some context on what time is for us and how it looks on the universal scale of things. All material bodies, from the sun to the atom, are under the influence of the kāla-chakra, or material time, but the scales of time for different bodies can be wildly different.
According to Srimad Bhagavatam, the smallest particles of material creations are called parama-aṇuḥ, or atoms. The smallest measurement of time mentioned there is the time of the chemical reaction that results in the combination of two atoms. Two parama-aṇuḥ’s combine to form an aṇuḥ (double atom) and three aṇuḥ’s combine to form a trasareṇuḥ (hexatom). The time needed for the combination of three trasareṇus, forming a trasareṇu-trikam (a molecule formed by 18 atoms) is called a truṭi, which equals about half a thousandth of a second.
100 trutis make a vedha, 3 vedhas make a lava, 3 lavas make a mimesa, 3 mimesas make a ksana, 5 ksanas make a kastha, 15 kasthas make a laghu, 15 laghus make a danda, and 2 dandas make a muhurta.
So far, we have thus:
100 trutis = 1 vedha
3 vedhas = 1 lava (300 truti)
3 lavas = 1 nimeṣa (900 truti)
3 mimesas = 1 ksana (2700 truti)
5 ksanas = 1 kastha (13,500 truti)
15 kasthas = 1 laghu (202,500 truti)
15 laghus = 1 danda or nadika (3,037,500 truti)
In modern times, a danda is calculated as being 1/30 of a day or night. It’s often taken as 24 minutes, but the length varies according to the seasons (as the days become longer or shorter). These values are used for astrological calculations.
However, the Srimad Bhagavatam appears to use a different value for the danda described in the text. Instead of being a variable unit that changes according to the length of the day, the danda mentioned in the Srimad Bhagavatam is a fixed unit, that can be calculated by a simple experiment involving a pot of copper on water described in SB 3.11.9. Different from the modern danda which is a variable unit of around 24 minutes, the danda mentioned in the Srimad Bhagavatam is a fixed unit that is calculated as approximately 30 minutes.
This makes sense, because all the smaller units are calculated according to the measurement of the danda, and it would not make sense they would become smaller or bigger according to the length of the day. A truti for example is a unit fixed at the time of a chemical reaction (that will take always the same time, regardless of the length of the day or night). In this way, we have:
One danda = 30 minutes
One laghu = 2 minutes
One kastha = 8 seconds
One ksana = 1.6 seconds
One mimesa = 0.533 seconds
One lava = 0.177 seconds
One vedha = 0.0592 seconds
One truti = 0.000592 seconds (1 second divided by 1,687.5)
From this, the Srimad Bhagavatam describes larger measurements of time. Two dandas make a muhurta and 3 muhurtas make a prahara. 8 praharas make an ahani or a set of day and night (24 hours). 15 ahanis make a pakṣaḥ (fortnight) and two pakṣaḥ make a masah (lunar month), which equals one day in Pitrloka. 6 masah make 1 ayanam (half year) and two ayanamas make a vatsaraḥ or lunar year, which is a day for the demigods. With this, we come to the scale of time we are used to dealing with in day-to-day life.
2 dandas = 1 muhurta (1 hour)
3 muhurtas = 1 prahara (3 hours)
8 paharas = 1 ahani (24 hours)
15 ahanis = 1 pakṣaḥ (fortnight)
2 pakṣaḥ = 1 māsaḥ (month) – one complete day and night in Pitrloka.
6 masah = 1 ayanam (half of the year, one complete movement of the sun from south to north.)
2 ayanam = 1 vatsaraḥ (lunar year) – 360 days, or one day and night for the demigods
Human beings live for 100 of such years. However, higher beings have much larger lifespans.
One year in Bhu-Mandala equals one day for the demigods. Therefore, one year for the demigods equals 360 years in Bhu-Mandala. Satya-yuga lasts for 4,800 years for the demigods, Tretā-yuga for 3,600 years, Dvāpara-yuga 2,400 years, and Kali-yuga for 1,200 years. Thus, a divya-yuga, or one complete cycle of four yugas lasts for 12,000 years of the demigods, or 4,320,000 years in Bhu-Mandala.
71 Divya-yugas, or complete cycles of four yugas, form a Manvantara (306,720,000 years, or 852,000 years of the demigods), and 14 Manvantaras, together with their sandyas form a day of Brahma (4.32 billion years). The same is the duration of his night.
1 Divya-yuga (set of 4 yugas) = 4.32 million years (12,000 celestial years)
1 Manvantara (71 Divya-yugas) = 306.72 million years (or 852,000 celestial years)
1 Kalpa (a day of Brahma) = 4.32 billion years
360 of such days and nights form one of his years, and 50 of such years form a parārdha. Brahma lives for two of such parardhas and thus his life is divided into two halves. As mentioned in SB 3.11.34: “The one hundred years of Brahmā’s life are divided into two parts, the first half and the second half. The first half of the duration of Brahmā’s life is already over, and the second half is now current.”
With this, we enter into the really big units of time:
2 kalpas (a day and night of Brahma) = 8.64 billion years
1 parardha (50 years for Brahma) = 155,52 trillion years
2 parardhas = 1 maha-kalpa (311,04 trillion years)
1 maha-kalpa (a life of Brahma) = 1 mimesa for Lord Maha-Vishnu
The total duration of the life of Brahma equals just one mimesa (about half a second) for Lord Maha-Vishnu, which gives us an idea of the insignificance of our limited lifespans in this material world. One could use these formulas to calculate how long are the ksanas, kasthas, laghus, and daṇḍas of Maha-Vishnu, but I believe what we saw up to here already makes the point.
Similarly, our universe is covered by seven layers (earth, water, fire, air, and ether, the total energy and false ego). The first layer has 10 times the diameter of the universe itself, and each successive layer has 10 times the diameter of the preceding layer. All the universes clustered together appear like atoms in a huge combination that are constantly created and destroyed, following the cycles of exhalation and inhalation of Maha-Vishnu. Thus, not only do we live for an insignificant amount of time, but we are also incredibly small on the universal scale.