Jyotish Diwas (Astrology Day) is being celebrated today based on the belief that Lord Brahma started time calculation on the day of Chaitra Shukla Pratipada in the Satya Yuga.The subject of time calculation beginning on Chaitra Shukla Pratipada is mentioned in the 'Brahma Purana' and is stated in the text 'Kaalmadhav' as follows:Chaitre Masi Jagadbrahma Sasarja Prathame'hani .Shuklapakshe Samagram Tu Tada Suryodaye Sati ।।Tada Pravartayamasa Kaalasya Gananamaapi ।।Meaning: On the first day of the bright half of the month of Chaitra, at the time of sunrise, Lord Brahma created the universe, and from that very moment, the calculation of time...