In different societies, depending on their requirements and practices - rituals, social and civil events - various calendar systems have evolved. These systems are essentially based on the solar year either tropical (savana) or sidereal (nakshatra) or lunar years (tithis or luni-solar).<ref name=":2">Rao, S. Balachandra. (2000) ''Indian Astronomy, An Introduction.'' Hyderabad: Universities Press (India) Limited. (Page 39-70)</ref> In the present times a Gregorian calendar is in use, almost globally, for all administrative and government records and events. | In different societies, depending on their requirements and practices - rituals, social and civil events - various calendar systems have evolved. These systems are essentially based on the solar year either tropical (savana) or sidereal (nakshatra) or lunar years (tithis or luni-solar).<ref name=":2">Rao, S. Balachandra. (2000) ''Indian Astronomy, An Introduction.'' Hyderabad: Universities Press (India) Limited. (Page 39-70)</ref> In the present times a Gregorian calendar is in use, almost globally, for all administrative and government records and events. |