India follows multiple regional Hindu calendar systems, each rooted in the same Vedic astronomy but adapted to local traditions. The Tamil calendar (Thiruvalluvar) starts in mid-April with the month of Chithirai, while the Bengali calendar (Bangabda) begins with Boishakh. Telugu and Kannada calendars follow the Chandramana (lunar) system starting from Chaitra, whereas the Gujarati calendar uniquely begins after Diwali.

Lunar vs Solar Calendars

South Indian calendars (Tamil, Malayalam) are primarily solar — months are tied to the Sun entering each zodiac sign (Sankranti). North and East Indian calendars (Bengali, Gujarati, Marathi) are luni-solar — months follow the Moon's phases with periodic intercalary months (Adhik Mas) to stay aligned with the solar year.

Vrat (Fasting) Observances

Ekadashi (11th lunar day) dedicated to Vishnu, Pradosham (13th day) for Shiva, and Sankashti Chaturthi (4th day) for Ganesha are the most widely observed recurring vrats. Purnima and Amavasya are significant for ancestor rituals and charity.