Hindu Calendar - History

History

The Hindu Calendar descends from the Vedic times. There are many references to calendrics in the Vedas. The (6) Vedāṅga-s (auto Veda) called Jyotiṣa (literally, "celestial body study") prescribed all the aspects of the Hindu calendars. After the Vedic period, there were many scholars such as Āryabhaṭṭa 5(th century CE), Varāhamihira (6th century) and Bhāskara (12th century) who were experts scholars in Jyotiṣa and contributed to the development of the Hindu Calendar.

The most widely used authoritative text for the Hindu Calendars is the Sūrya Siddhānta, a text of uncertain age, though some place it at 10th century.

The traditional Vedic calendar used to start with the month of agrahayan (agra=first + ayan = travel of the sun, equinox) or Mārgaśīṣa. This is the month where the Sun crosses the equator, i.e. the vernal equinox. This month was called mārgashirsha after the fifth nakshatra (around lambda orionis). Due to the precession of the Earth's axis, the vernal equinox is now in Pisces, and corresponds to the month of chaitra. This shift over the years is what has led to various calendar reforms in different regions to assert different months as the start month for the year. Thus, some calendars (e.g. Vikram) start with Caitra, which is the present-day month of the vernal equinox, as the first month. Others may start with Vaiśākha (e.g. Bangabda). The shift in the vernal equinox by nearly four months from Agrahāyaṇa to Caitra in sidereal terms seems to indicate that the original naming conventions may date to the fourth or fifth millennium BCE, since the period of precession in the Earth's axis is about 25,800 years.