The Amavasya is the fifteenth day of the dark half of lunar month, on which day the sun and moon are in conjunction. Amavasya is the Indic name of new moon. The Amavasya is based on lunar calendar, which is the part of thirty-day lunar cycle. Amavasya or the new moon is the last day of the waning moon. The amavasya is important for performing the rituals for the departed ancestors.

Vishnu Dharma Shashtra states that Amavasya is the day for the Pitrus, or souls of the forefathers. This day is auspicious and is dedicated to the remembrance or worshipping of the forefathers. However, no travel should be done on the days of Amavasya , as traveling without moonlight was forbidden in the ancient days.

There are some legends related to Amavasya. One of the stories is that of Acchoda, who was the mentally conceived daughter of Barhishadhas. Since Acchoda did not have a father, she always coveted for a real father. As a result of her mortal desires, she lost all her divine and Yogic power and fell from heaven. While she was falling she prayed to be saved. The souls from Pitru Loka (the world of forefather) heard her appeal while she was passing though the `PitruLoka` and they immediately came to her rescue. They heard her story and advised her to be born as King Amavasu`s daughter. King Amavasu was a wise, judicious and erudite man.

Later on things happened as the Pitrus predicted. In the mean time Acchoda regained her powers. Acchoda arranged a ceremony to remember the Pitrus.

Amavasya is named after King Amavasu. On this day the custom of honouring our forefathers is observed since the ancient days. Pitru Karma is observed to plea the forefathers to safeguard from any hindrances and also to seek their blessings.

People also conduct `Poorna Kriya` on the Amavasyas. This is generally connected with the birth of twins. The ceremony brings contentment and peace to the life of twins.

Somavati Amavasya or Somavara Amavasya is associated with the new moon, which occurs on a Monday. The Mondays, which are new moon days are considered to be very auspicious as Mondays are days of moon. People keep Vrata and observe fasting on Somavati amavasya for the longevity of their spouses.

Saamba Parameshwara Pooja is also performed on the Amavasyas to appease Lord Shiva. The dark fortnight of aswayuja (September- October) is known as Mahalaya Paksha. The fortnight is especially sacred for offering oblations to the departed forefathers. The last day of this waning period of moon is considered as most important day in the year for performing the rituals. There is also a legendary story behind it.

When Karna, the great hero of Mahabharata left his mortal coil he ascended to the higher worlds as he by the time did gather many virtues by his great charity, which now returned to him in hundredfold. But all he donated was gold and silver and as he did not do any food-charity, he had no food to eat. He prayed to Yama, the god of death so that he could return to the earth for fourteen days to make up his deficiency.

When Karna returned to earth, for fourteen days he fed Brahmins and poor and offered oblations of water. On return to the higher regions, he got food in plenty. These fourteen days are commemorated as the Mahalaya Paksha. It is believed that due to grace of Yama, all offerings made to ancestors in the Amavasya fortnight, reach their souls very easily.

Those who are the worshippers of Surya recognize Amavasya as powerful and auspicious, while Chandra or moon worshippers consider the day as unsuitable one.