The deśāntara is the distance (antara) of a place (deśa) toward the east or the west of the prime meridian. It is, in other words, the terrestrial longitude of a place. In Indian astronomy, the meridian passing through the city of Ujjaini (modern Ujjain) in the central Indian state of Madhya Pradesh was identified as the prime meridian. Extending from the North Pole to the South Pole, it cut the equator at a point where the astronomers imagined the existence of a city called Laṅka. The Ujjaini meridian is located at 75° 45′ east of the modern prime meridian at Greenwich.
The deśāntara was generally expressed as a time measure rather than as the angle subtended at the pole by the meridian of the place and the prime meridian. This was done to enable the local time and the time at the prime meridian to be converted into each other. Time measures used in India to determine the deśāntara included the nāḍī or the ghaṭī (1/60th of a day or 24 min), the vinādī (1/60 nādīs or 24 s), and the prāṇa...
- Balachandra Rao, S. (2000). Indian astronomy: An introduction (pp. 82–86). Hyderabad: Universities Press.Google Scholar