Dear Sangom, I have discussed the above question with my Vaadiyar who is a First class graduate and a gold medalist from Kanchi Patashala. As per him, Tharpanam is to be performed from the first year itself. he said even if Tharpanam falls on 13th day from the date of death, the Karta is required to perform Tharpanam in the morning and perform all other rituals later in the day. Thanks.