The Indian era has been calculated from the beginning of the earth. This has been done on the basis of `kalpas'. A kalpa is one day in the life of the Brahma. Each day of the kalpa consists of 432 crore years. Ancient Indian astronomers `fixed' Brahma's age at 100 years and made their calculations accordingly. Tradition has it that the universe begins and self-destructs in one kalpa of the mighty Brahma. And, the kalpa is subdivided into 14 `manvantaras'. Six manvantaras out of the 14 are already over and done with and we are now into the seventh (Vaivasvata, in which the Hindu law giver Manu was born).We are experiencing the 28th `mahayug' of that manvantara at present.

But more classifications were made by the ancient seers, which further divided each manvantara into 71 mahayugas and each mahayuga into four `yugas'- Kruta, Treta, Dwapara and Kali. Kruta yuga consists of 17,20,000 years. Treta consists of 20,96,000 years, Dwapara 8,64,000 years and Kaliyuga 4,32,000 years.

The Hindu calendar, which ranks on par with the Chinese one in terms of antiquity, is now in the thick of the Kaliyuga, 5100 years of which would be completed tomorrow.

From Thursday the 52nd century would begin. This year is called `Pramathi'. According to this almanac, there are 60 names for years which keep rotating. This is considered to be the most incisive time calculation in the world.

It is to the credit of ancient Indian astronomers and mathematicians like Varahmira, Bhaskara, Aryabhatta that calculating errors on the basis of this ancient calendar have proved to be negligible. So much so that in the absence of moderngizmos these `scientists' managed to divide the second into minutiae like the `truti', the 33, 750 part of a second. These calculations are still being used to predict solar and lunar eclipses, sunset, sunrise, etc.

According to Jyotishacharya (Mrs) Vidya Arun Rajendekar these astronomical calculations are still followed religiously by Indians especially by farmers for predicting onset of the monsoon and changes in season.