Please accept my blessings. I have seen your letter dated August 31, 1975 regarding the calculation of my birthday. The system for calculating is as follows: the first day of birth is the first birthday. The next year that day is the second birthday; i.e. the second birthday means that one year has been completed. So it is my 80th birthday, and I have completed 79 years.
According to the Hindu system, on the first birthday there is jata karma ceremony and all big, big astrologers assemble and give the horoscope. In the Srimad-Bhagavatam the birthday of Maharaja Pariksit is there.