The thought of the year brings into the minds of many the fear and images of gloom, doom destruction and death. In the past year there have been countless books, movies and discussion being carried on the destructive stories which are now being proved as completely false by the panchangam. Indian sages were very good with astronomy, spirituality, medical science and so many other fields. The panchangam they made were based on the daily movements of the sun and the moon at the time of sunrise during the year. This knowledge is passed down from generation to generation and the calendar that is prepared every year accordingly and we commonly call it as panchangam.
The panchangam calculation is based on two important heavenly bodies that are known as the sun and the moon. There are various ancient methods used by the sages to calculate panchangam and the very ancient one is known as Surya Siddhanta, another one is Vakyam Siddhanta, and the last one is Driga Ganita. The Vakyam is an ancient system where planetary motions are described in simple sentences and hence known as the vakya. The author of Surya siddhanta clearly mentions that one should observe the sky and make necessary corrections to planetary formulae so that you can make an accurate panchangam
We have different panchangam for different cities and once you buy a panchangam from India you can use it anywhere in the world. But however this is a wrong practise because people abroad can make wrong calculations and misunderstand a festival on a wrong day or time in abroad. Each festival has a different set of rules of how to observe them. Hindu festivals are generally based on the tithi or nakshatra as per the lunar calendar and some as per the solar calendar.
Each tithi begins and ends at the same instant all over the world. After correcting the time zones, the tithi will begin and end at different times in different parts of the world. However you should make sure that tithi is visible during the specified time. This is done by people by using the local sunset, local sunrise and local moonrise. India how ever has a little variation in terms of sunset/sunrise and therefore panchangam computed for one area of the country is generally used throughout the country. The panchangam will also have two Ekadashi rules like every other calendar – The Smarta and Vaishnava.
The smarta rule is simple and says that ekadashi is visible at the time of local sunrise. Whereas vaishnava agrees that ekadashi is not contaminated by dashami tithi. Ekadashi should be prevailing two hours before sunrise. If you follow the Indian panchangam abroad, apply the standard time differences, so ekadashi might fall on a day before India and therefore people end up fasting on some other day rather than ekadashi. Therefore to conclude it would be best to use Drika panchangam for the current year, as using any panchangam used in India will not be a good idea.