The Hindus have had from very ancient times the system of lunisolar cycles, made by the combination of solar years, regulated by the course of the sun, and lunar years, regulated by the course of the moon but treated in such a manner as to keep the beginning of the lunar year near the beginning of the solar year. The exact way they arranged the details of their earliest Calendar is still a subject of research. We deal here with their Calendar as it now stands, in a form developed from about A.D. 400 under the influence of the Greek astronomy introduced into India at no long time previously.