Calendars are created by civilizations to give a meaning to the continuous flow of time, according to their world-views. India has developed it's own unique collection of many calendars for regulating it's religious and cultural life. The current book presents a comprehensive account of their structure and relative importance at present and places them in the context of other calendars prevalent outside India. Suggestions have also been made for making some changes to bring them in line with our current astronomical knowledge. This book will be very useful for students, researchers and anyone else who is curious about the calendars.