History of Indian and European Calendars (Timekeeping): Difference in Definition of a Year

Anand M. Sharan

Calendar, Effect of precession, Tropical calendar, Sidereal calendar, Time period of a year

Abstract: This paper discuses Indian and European calendars used since ancient times. The paper shows that the Indian calendar included sidereal as well as tropical year information. On the other hand, the European ( Julian ) calendar did not include the processional motion of the earth’s axis. This calendar was reformed in 1582 AD by Pope Gregory but this calendar changed from a sidereal to a tropical calendar which is about 20 seconds shorter than a sidereal calendar.

In India, Gregorian calendar was adopted during the British rule but its use remained amongst the educated masses in the cities. The students in schools and universities in India have not been taught accurately the difference between a sidereal and a tropical year.