Episode 8: Why do Hindu festival dates (such as Diwali, Navaratri) change from year to year?

Описание: Why do Hindu festival dates change from year to year?

Simple answer is, they do not. Hindu festival occur on the same date, year after year, on the Hindu calendar but they do change from year to year on the Christian calendar!

For instance:
Naga Panchami occurs on Shravana masa, Shukla paksha, Panchami tithi every year.
Ganesha Chaturthi occurs on Bahdrapada Masa, Shulka Paksha, Chaturthi tithi every year.
Navaratri begins on Ashwina masa, Shukla paksha, Prathama tithi, and ends on Ashwina masa, Shukla Paksha, Dashami tithi (Vijaya Dashami) every year.

If a festivals occurs during Krishna paksha, then the followers of Amanta and Purnimanta tradition will say the festival occurs on different months, though they celebrate it on the same identical day! This follows from the definition of Amanta and Purnimata traditions.

For instance, as per the Amanta tradition, Naraka Chaturdashi occurs on Ashwina masa, Krishna paksha, Chaturdashi tithi every year; but as per the Purnimanta tradition it occurs on Kartika masa, Krishna paksha Chaturdashi every year. Though the months are different, both refer to the exact same day!

There are some occasions when a Hindu festival may indeed occur on different days in successive years, even on the Hindu calendar. This is because most tithis span across two solar days. By convention, the tithi is associated with a solar day depending on the position of the Moon at sunrise. But Hindu priests may determine the auspicious "Puja Muhurtha" as being more appropriate on the previous solar day. The exact details of how puja muhurtha is determined is beyond the scope of this series.

0:00 Opening narration
7:10 A real Hindu calendar
12:16 How to generate a Hindu calendar from drikpanchang.com
14:30 Naga Panchami
18:30 Ganesha Chaturthi
20:43 Navaratri
23:55 Naraka Chaturdashi (a festival in Krishna paksha)
27:38 Dhanteras (variation of festival date by a day)
34:39 Closing narration