Utpal Mukhopadhyay obtained his MSc degree in Applied Mathematics from the University of Calcutta in 1986 and since then he is serving as a teacher of Barasat Satyabharti Vidyapith. He is actively engaged in science popularisation programme and regularly writes popular and semi-popular articles on astronomy, mathematics and physics in various journals of India and abroad.

Just like the axis of a rotating top, the axis of the Earth moves in a conical path about the ecliptic pole and completes it in about 25800 years. This motion of the Earth is known as precession. Due to this precessional motion, the equinoctial points experience a westward motion and hence the cardinal points shift their positions with the passage of time. In this article, the causes of precessional motion and its effect on calendar preparation are discussed.

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Address for Correspondence

Utpal Mukhopadhyay
Teacher, Baraat Satyabharati Vidyapith
P B Nabapalli, Dist
North 24-Parganas
West Bengal 700126, India.