Guide
How the calendar decides the dates — and the choices that you, the user, make.
Mayapur or your location? Pre-1990 and post-1990 standards
One setting decides on which date you celebrate festivals and keep Ekādaśī. Please read this page once, and choose consciously.
Vaishnava or Smārta Ekādaśī?
Why is Ekādaśī in this app sometimes a day later than in my other calendar? It is not an error: two traditions count Ekādaśī by different rules.
How the festival day is counted
Two questions decide on which day a festival or an Ekādaśī fast falls: where the day is counted, and what the tithi is at sunrise and at Aruṇodaya.
Celestial and Earth-sky horizon
The app can calculate sunrise for two kinds of horizon. Vaishnavas use the Celestial one — and here is why.
Śrī Navadvīpa Pañjikā
By Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura. English translation by Manoj Mitra. This is the Pañjikā whose rules the Vaishnava Calendar for ISKCON follows.
Accuracy of Tithi and Sunrise computations
The app and GCAL validated against the JPL DE421 ephemeris.