section_path: Astronomical basis
section_name: Astronomical basis
paragraph_text: Astronomical basis
  
  The Hindu calendar is based on a geocentric model of the Solar System. A large part of this calendar is defined based on the movement of the Sun and the Moon around the Earth (saura māna and cāndra māna respectively). Furthermore, it includes synodic, sidereal, and tropical elements. Many variants of the Hindu calendar have been created by including and excluding these elements (solar, lunar, lunisolar etc.) and are in use in different parts of India.