Panchak in Sanskrit means a group of ‘Five’. Starting from Dhanistha - 2nd quarter, the last five Nakshatras Shatbhishaj, Poorvabhadrapada, Uttarbhadrapada and Revati on the Zodiac belt are known as Panchak. These Nakshatras fall in Aquarius and Pisces signs. Panchak occurs every month when Moon transits through Aquarius & Pisces Signs. For the mathematical minded this happens when Moon's longitude measures between 296 degrees and 360 degrees in sidereal calculation. Hindu philosophy believes that no auspicious work should be undertaken during this period. Auspicious events like marriage, welcoming a new Bride, Mundan and Upnayan Sanskar, starting construction and entering a new house are prohibited during this period. If a person dies during Panchak, a Shanti Pooja is performed for the departed soul as well as for the family left behind.
Following five activities are completely prohibited during Panchak. Marriage, starting something new, traveling in south direction, stocking up with fuel, and cremation of a dead person are not done during Panchak.
Garuda Purana says that "Person who dies during Panchak does not get peace and it is not good for the family left behind."
There is a prevalent belief that if one performs any important task during these Nakshatras one may end up doing it five times.
The Panchak Nakshatras are not considered during the festivals of Raksha Bandhan and Bhaiya Dauj.