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.

Most of these calendars are inherited from a system first enunciated in Vedanga Jyotisha of Lagadha, a late BCE adjunct to the Vedas, standardized in the Surya Siddhanta (3rd century CE) and subsequently reformed by astronomers such as Aryabhata (499 CE), Varahamihira (6th c. CE), and Bhaskara (12th c. CE). Differences and regional variations abound in these computations, but the following is a general overview of Hindu lunisolar calendar.

In the Hindu calendar, the day starts with local sunrise. It is allotted five "properties", called angas. They are:

Together these are called the panchāngas (Sanskrit: pancha = five). An explanation of the terms follows.

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