The universal cycles

The ages are periods of time measured according to the life cycle of the first created being in the universe, Brahmā. From the perspective of human beings, Brahmā seems immortal; he lives as long as the universe exists. He leaves his body when the universe is destroyed.

Brahmā lives for 100 years according to the calendar of his planet, Brahmā-loka.

One day in Brahmā's life lasts 1000 cycles per 4 ages on earth.
The age we are living in now is the last of a cycle of 4 ages
and 1000 such cycles are one day in the life of Brahmā.

This age is called Kali Yuga because the predominant deity of this age is an evil deity who is tasked with destroying the Vedic civilization, which he will achieve 100% by the end of the age.
Kali-yuga is the worst of all 4 ages where human beings become weaker and weaker.

At the beginning of this age of Kali only ¼ of all good qualities of the first age Krita- or Satya-Yuga (age of truth and virtue) are still present and at the end of Kali-Yuga all good qualities go to zero.

This age lasts only 1000 years, according to the calendar of the gods, who also seem immortal from a human perspective; one day on the planets of the gods is described as having ½ year on earth and that is exactly how long their night lasts. Some gods live for about 10,000 years, according to their calendar - 3,600,000 earthly years.

One year of the gods is calculated as 360 years on earth.
Thus Kali-yuga lasts about 360,000 earthly years.

Before and after this age, as before every other age, there is a transition period lasting 1/10 of the actual age; these transitional periods are counted towards the actual Kali Yuga;
that means 100 heavenly years for the "ramp-up" and 100 years for the "ramp-down" of Kali-yuga.
In the transition period, when Kali-yuga is shut down, for about 100 years according to the counting of the gods (36,000 earthly years), all human beings, who will be on average about 30 cm tall, will be exterminated and a new earth will appear with new inhabitants described as giants in the manifestation of virtue and living for about 100,000 years, as the Satya-Yuga is ramped up.

Satya-yuga lasts 4000 years according to the calendar of the gods,
plus 400 years each transition period.

So, Satya-yuga lasts a total of 4800 heavenly years - 1,728,000 earthly years.
During this time, spiritual perfection is most widely practiced as yoga meditation.

This is followed by Treta-Yuga, which lasts 3000 years according to the calendar of the gods,
plus 300 years each for transition period.

Treta-yuga lasts a total of 3600 divine years - 1,296,000 earthly years.
Spiritual perfection is highly publicized as great sacrificial ceremonies.

All good qualities are cut by ¼ and people only live for 10,000 years, appearing small in comparison to those of Satya-Yuga.

This is followed by Dwapara-Yuga, which is 2000 years after the reckoning of the gods,
plus 200 years each for transition period.

Treta-yuga lasts a total of 2400 heavennly years - 864,000 earthly years.
Spiritual perfection is most widely practiced as worship of the image of the gods.

All good qualities still atone for another ¼ and people only live for about 1,000 years and appear small in comparison to those of Treta-yuga.

This is followed by Kali-yuga, which is 1,000 years after the counting of the gods,
plus 100 years each for transition period.

Kali-yuga lasts a total of 1200 heavenly years - 432,000 earthly years.

Spiritual perfection is highly prevalent as the praise of the names of the Transcendental Lord.

All good qualities are still atoning ¼ and people only live for about 100 years and appear as dwarfs compared to those of Dwapara-Yuga.

A cycle of 4 ages lasts 12,000 heavenly years according to the calendar of the gods:

Krita Yuga - 4000 + 800 +
Treta Yuga - 3000 + 600 +
Dvapara Yuga - 2000 + 400 +
Kali-Yuga - 1000 + 200

So in the case of the Mahabharata, Nilesh Nilkanth Oak analyzed more than 200 astronomical observations, sometimes individually, sometimes in groups, and came up with the year 5561 BC as the year of the Mahabharata war.

https://sangamtalks.org/dating-of-ramayana-and-manabharata-a-talk-by-nilesh-oak/

Kali-yuga began around 7500 years ago, when the Transcendental Lord Krişna, left the earth.
After Kali-Yuga, the cycle comes to an end ... and begins again with Krita-yuga, the age of truth and virtue.