If somebody reads the Pangika in Bengali ,will feel the true concept of total Bengali [also Indian ] festivals. The importance of this is, it reflects all the minors[so called] festivals of astronomical changes also. And not only that it gives us the information about the birth and date of demise of eminent all Mahapurusas including religious and social. Not only this is for only The Hindu, all religious festivals of all Religions in India and information it bears.
This is a very useful book/guide for India's day to day's life.
We the modern Indians ,some of us though follow it ,at least some times, most of us do not see that our Hindu rituals are all dependent on astronomical calculation and depends on stellar positions. We follow both Solar and Lunar phenomena. Why and how ,it becomes clear with this Pangika. We are advancing in science but these guidelines we hardly can disobey in social life; even in most communist family also. Rather I think it is becoming more accurate with modern science.
But I pay homage to those brains who calculated all these without any modern devices,and only with mathematics.
As always I'm greatful to GOOGLE for images.