Due to this dominance of India in all fields, for the last few 1000s of years, the world’s #PrimeMeridian was passing through India. The Zero meridian then passed through Avantika, the ancient name for present day #Ujjain. 
This meridian passing through Ujjain, starting from North Pole & passing all the way down to the South Pole, has been repeatedly mentioned by many of the ancient geographers of India and the world. Notable among them are Aryabhatta, Varahamihira, Bhaskaracharya etc.
In medieval India, Bhaskaracharya in his Laghubhaskareeyam, verse 1 -23, mentions
“That line which passes through Lanka, Vatsyapura, Avanthi, Himalaya, Suraalaya is known as the International Meridian line.”
“That line which passes through Lanka, Vatsyapura, Avanthi, Himalaya, Suraalaya is known as the International Meridian line.”
Varahamihira in 530 C. E, in his Pancha Siddhantika, verse 9-10, on the Time correction from meridian, states that
“1 nadi for every 53 1/3 yojana has to be deducted or added by the people in the east and west respectively of the Ujjaini meridian.”
“1 nadi for every 53 1/3 yojana has to be deducted or added by the people in the east and west respectively of the Ujjaini meridian.”
In those days, the Maha Kaleshwara temple in Ujjain was the marker point.
Maha means great, Kala means time & Eashwara means controller. So this temple of Maha Kaleshwar in Ujjain represented the control mark for calculating & keeping track of time for the globe, in yester yrs.
Maha means great, Kala means time & Eashwara means controller. So this temple of Maha Kaleshwar in Ujjain represented the control mark for calculating & keeping track of time for the globe, in yester yrs.
