Shastabdi poorthi means completion of 60 years. This function is held when a married man reaches this milestone if at that time his wife is also alive. May be in the earlier years when the average life span was very low this used to be an enviable milestone and people were naturally worried about the evil eyes. The function is therefore aimed at ensuring a healthy long life warding off the effect of evil eyes.
There are many variations in the style and even time of celebrating this function in different regions of India and also by different families in the same region. In our family the tradition is to celebrate it in the 60th year before the completion of the 60th year. In Tamil nadu the practice is to celebrate on the day the 60th year is complete. In some families they go on a pilgrimage in the 60th year for this purpose instead of performing homas in their houses. In the practice that is followed in our family the interesting part is the "Mangalya Dharana", which provides a chance for the children to witness a sort of re-marriage of their parents. The rituals done in the Shanthi function for Ramesh and Pommi is attempted to be reproduced here as a sort of indication of our family tradition. Here again there can be variation from time to time depending on the circumstances and the Purohit.
(The above is an unedited version issued in a hurry to meet the press deadline and will be corrected and improved upon shortly)