Sanatani Panjika

History of the panjika

The tradition of timekeeping in the Indian subcontinent is thousands of years old. In the Vedic age, lunisolar reckoning was used for yajnas and season-based agriculture. Later the ancient astronomical treatise 'Surya Siddhanta' became the basis of panjika calculation, mathematically determining the paths of the sun, moon and planets.

In the modern era the 'Drik Siddhanta' method developed on the basis of actual astronomical observation, which is more accurate than the Surya Siddhanta. In the Bengal region the Gupta Press and Bishuddha Siddhanta panjikas carry this tradition and are still used to fix the dates of religious festivals and vratas.

The four calendar systems and how they relate

The MandirBD panjika shows four calendars at once — the Sanatani Bengali era, Vikram Samvat, Bangladesh's official Bengali era, and the Gregorian (English) year. Each system has a different basis of calculation, so the date for the same day can differ across the four.

The Sanatani Bengali era is a solar calendar that depends on the sun's entry into a zodiac sign, i.e. the sankranti, while Vikram Samvat is a lunar-month-based era running roughly 57 years ahead. The Gregorian calendar is entirely solar and used internationally.

Bangladesh's official Bengali era is a reformed solar calendar with fixed month lengths. Seeing these four systems side by side lets devotees easily reconcile religious tithis with everyday dates.

Bangladesh's revised Bengali calendar

In 1966 the Bangla Academy, led by Dr Muhammad Shahidullah, proposed a reform of the Bengali calendar in which the first five months were fixed at 31 days and the rest at 30 days. The aim of the reform was to keep the dates consistent with the Gregorian year.

It was revised again in 2019 to fix Pohela Boishakh and the national days to specific English dates. As a result the official Bengali date is now a fixed solar calendar, which usually differs by one or two days from the sankranti-based Sanatani panjika — which is exactly why the two dates do not match.

How tithi and paksha are determined

A tithi is completed when the angular distance between the sun and moon crosses 12 degrees. Since the moon's speed is not uniform, the length of a tithi varies, and a tithi may be shorter or longer than one English day. That is why the panjika lists the specific start and end time of each tithi.

Ekadashi, Purnima, Amavasya and Sankranti are the special days of the panjika. Fasting on Ekadashi, special puja and tarpan on Purnima and Amavasya, and the start of a new month on Sankranti — knowing all these correctly requires daily tithi calculation.

How the MandirBD panjika is calculated and verified

The MandirBD panjika determines the tithi, nakshatra, yoga, karana and sun-moon timings on the basis of astronomical calculation, and where possible publishes the information after verification by an experienced pandit. Each day shows the reliability of its source and its verification status, so devotees can trust the data.