English meaning of the festival
Panchak is a phase of five days or a group of five. It occurs when moon is present in the last two Zodiacs (Aquarius & Pisces). Panchak occurs every month.
How the date is decided annually
The date and times of Panchak are calculated when the moon transits from Aquarius to Pisces and continues for approximately 5 days.
Significance of the festival to Hinduism
Panchak Nakshatra are specific to death. The Panchak Nakshatra are Shathabish, Dhanishta, Purvabhaadrapad, Uttarabhaadrapad and Rewathi. A Panchak Shanthi Pooja has to be performed on the day of the funeral and on the 12/13th day. While some believe that the time of cremation is used to determine whether to do this Panchak Shanthi, others believe it should be done either if death or of cremation occurred during Panchak.
How to observe/practice
The vidhi or procedure for this Panchak Shanti Pooja is elaborate and requires the services of a Priest. In short on the day of the funeral four “corpses/bodies” made of Koos are cremated with the deceased. Hawan mantras pertaining to the specific Panchak Nakshatra (Shathabish, Dhanishta, Purvabhaadrapad, Uttarabhaadrapad and Rewathi) in which death occurred and/or cremation is taking place is recited during the final rites.