The origin of the Hindu calendar can be traced to the Vedic literature. Srauta Sutra of Katyayana (3rd – 4th Century BCE) as well as Nidantasutra of Sama Veda, and Vedanga Jyotisha are significant text in this context. These are some of the oldest reference of Hindu calendar. Listed in them are several ways to measure the day, month, and year and two calendars – lunar and solar. A solar year, which governs the seasons, is defined as the time taken by the sun to travel through the twelve signs of the zodiac. The lunar calendar consists of about 29.5 days a month and 354 days a year, and so the lunar months go out of a step with the seasons in the course of few years. So after a regular period a thirteenth month called intercalary month, is added to the year. Based on these features, the structure of the present Hindu calendar was fixed during the siddhanta period.
The Hindu calendar also mentions some eras like Saptarishi Kala (the cycle of Seven Sages), which is said to go back to 4077 BCE or 6777 BCE. This era is named after the seven stars of constellation of the Great Bear.
Brihaspatya Kala (cycle of Jupiter) is a period of sixty years. This era was in use before Christian Era, as references to the names of the sixty years of the cycle are found in many inscriptions.
The Kali Yuga, or the fourth age of the Hindu chronology, dates back from 3102 BCE. The era of Kali Yuga is certainly found in the astronomical works down to the time of Aryabhata (476 CE) and Varahamihira (505 CE).
The Parashurama era, which was popular in Southern India, is a cycle of one thousand years, said to have begun in 1176 BCE. Another era popular in this region was the graham parvati cycle which began in 24 BCE.