Hindu calendar

Lore & Background

The Hindu calendar's conceptual design is also found in the Babylonian, Chinese, and Hebrew calendars, but differs from the Gregorian calendar. Unlike the Gregorian system, which adds extra days to months, the Hindu calendar inserts an extra full month every 32.5 months on average to keep festivals and crop-related rituals in the appropriate season. The calendar maintains the integrity of the lunar month while using the solar cycle to define the year.

Regional variations exist: the Shalivahana Shaka (basis for the Indian national calendar) and Vikram Samvat emphasize the lunar cycle, with their new year starting in spring. In Tamil Nadu and Kerala, the solar cycle is emphasized in the Tamil and Malayalam calendars, which originated in the second half of the 1st millennium CE. The Buddhist and Jain traditions also use lunisolar systems based on older versions of the Hindu calendar.

Hindu scholars refined the calendar through astronomical texts such as the 5th-century Aryabhatiya, the 6th-century Romaka and Panca Siddhantika, and later works by Brahmagupta and Lalla. These texts calculated the sidereal year length and tracked solar and lunar movements with sophisticated rules, including intercalary months added every 32.5 months on average.

Reader's Guide

The Hindu calendar is significant as one of the oldest continuously used lunisolar systems, with roots in Vedic timekeeping and Jyotisha, one of the six Vedangas. Its influence extends beyond Hinduism: early Buddhist communities adopted the ancient Vedic calendar, and the traditional calendars of Cambodia, Laos, Myanmar, Sri Lanka, and Thailand are based on an older version of the Hindu calendar. Jain traditions also follow the same lunisolar system. The calendar's astronomical basis, refined during the Gupta era by scholars like Aryabhata and Varahamihira, demonstrates advanced ancient Indian understanding of celestial motions, including calculations of the Earth's diameter close to modern values. The Vikrami calendar, named after King Vikramaditya and starting in 57 BCE, remains widely used in Nepal and northern India. The calendar's legacy includes its role in setting festival dates, fasting days like Ekadashi, and its integration into Hindu astrology and zodiac systems. Regional diversification in the medieval period produced variants still in use today, such as the Balinese saka calendar in Indonesia.

Did You Know?

• The Vikrami calendar is named after king Vikramaditya and starts in 57 BCE.
• Aryabhata's circumference estimate yields a diameter of about 12,717 km, a remarkable early approximation of Earth's size.