This book is the outcome of the project meticulously carried out by Prof. R. Parthasarathy (Retd. Prof. of Geography, D.B. Jain College, Chennai) under the "Om Namashivaya" project instituted by Arutchelvar Dr. N. Mahalingarn.

Dr. N. Mahalingam had been initiating different but connected research investigations into our ancient history through astronomy and he sought the help of our Institute to prove or disprove the findings of one of his recent researcher’s Sri N.P. Rarnadurai in this regard. Dr. Mahalingam was a shrewd assessor of men and matters; he was sure that Sri N.P. Ramadurai had started a spark but seemed to feel that it was not in the proper direction. He approached the Institute to appoint some scholar to go through the work and give his sincere opinion.

Accordingly, Prof. R. Parthasarathy worked on this and with his knowledge of Sanskrit, Astronomy and Geography he was able to throw more light on the subject.

In the second meeting, Dr. Mahalingam came with an idea of concentrating on the Caturyuga Calendar and fix the history of India as found in the Puranas within the limit of 3,00,000 years. This took well with all of us; in fact, it made us think on these lines for the first time and found that there is much in this thought process of Dr. N. Mahalingam.

Dr. Mahalingam was quite enthusiastic about this and he advised Prof. Parthasarathy to work 'on an independent project on Caturyuga Calendar. The result is presented now to the public in the form of this book.

Prof. Parathasarathy had to consult the Ithihasas and all the major Puranas and other texts while culling out relevant information on this subject. Realising the importance of this study, the research.