The hindu calendar used in ancient times has undergone many changes in the process of regionalization, and today there are several regional Indian calendars, as well as an Indian national calendar. Nepali calendar, Bengali calendar, Malayalam calendar, Tamil calendar, Telugu calendar, Kannada calendar etc. are some prominent regional Hindu calendars.
The Hindu calendar follows the lunar year that consists of 12 lunar months. The earliest Hindu calendars derived from Gupta era and were developed by Āryabhaṭa and Varāhamihira in the 5th to 6th century. The Hindu calendars have undergone many changes in the process of regionalization. Some of the more prominent regional Hindu calendars include the Nepali calendar, Punjabi calendar, Bengali calendar.