Stellar Antiquity

The Vedic civil calendar was a luni-solar calendar and played a major role for agriculture and religious rituals. The solar year was known to have a little over 365 days, but in the Vedic calendar a solar year had 360 days, divided into 12 months of 30 days each. An intercalary month (a 13th month of 30 days) was added every 5 years in order to help harmonize the lunar and solar year. The period of 5 sidereal years or 62 lunar synodic months was called a yuga (not to be confused with epoch) and had 1830 days.

The year had 6 seasons, each season lasting for 2 months:

Vasanta (spring) during the months of Madhu and Madhava

Grishma (summer or the ‘hot’ season) during the months of Sukra and Suci

Varsha (monsoons or the ‘rainy’ season) during the months of Nabha and Nabhasya

Sharad (autumn) during the months of Isa and Urja

Hemant (winter) during the months of Saha and Sahasya

Shishir (the ‘cool’ season or freeze) during the months of Tapa and Tapasya.

Each sidereal year was also divided into two halves based on the direction of the sun’s travel. When the sun traveled north, the time of year was called uttarayana; when the sun traveled south, the time of year was called daksinayana.

Reference:

Lagadha. 1984. Vedanga Jyotisa of Lagadha. Translated by T.S. Kuppanna Sastry. New Delhi: Indian National Science Academy

Kak, Subhash C. (2000). ‘Birth and Early Development of Indian Astronomy’. In Selin, Helaine (2000). Astronomy Across Cultures: The History of Non-Western Astronomy (303-340). Boston: Kluwer. ISBN 0-7923-6363-9.