The Hindu calendar also called as the Panchanga or five parts is an ancient time reckoning system that is used to determine the dates of the Hindu festival. This lunisolar calendar can have many regional variations. This calendar was developed in ancient India by learned scholars. The earliest known description of these can be found in the Vedas and some of these dates to 1200 BCE.
Keeping along with the balance of the leap year, an intercalary month called as the Purushottam Maas is added when lunar month starts and ends before Sun's progression to the next zodiac sign. In rare instances, the Sun traverses a whole zodiac sign then the month is removed completely from the calendar.