It starts from the Full Moon Day or one day after the Full Moon Day in the month of Bhadrapada and ends on the No Moon Day.
Mahalaya Paksha is known as Pitru Paksha. It is the time for paying obeisance to our ancestors who are in the Pitru Loka.
Offering shraddha, dhanam, tarpanam on all the days from September 6 to September 19 is necessary to help our ancestors move into heaven.
By doing tarpanam and Pitru Seva during this time, people who suffer from Pitru Dosha get rid of their sufferings in life.
A person is able to complete the unfulfilled desires of his dead ancestors through paying obeisance to them during Pitru Paksha.
Suppose an unnatural death has occurred in the family, appeasing the ancestors through Pitru Seva during this time does good for the family.
It is believed that one of the ancestors comes down to the earth during this time and blesses his family members. Doing oblations to the ancestors works well for the family.
As per legends, Lord Karna who did not offer Pitru Seva in his life on earth came back to earth after his death during this time to offer oblations to his ancestors.
Mahabharani, Ashtami and Sarvapithri Amavasya are the days important for Pitru Seva.
Performing tarpanam on all the days will bring very good results.
Thithis of the father and the mother
Mahabharani- (September 10, Sunday)
Mahavyathipatham- (September 14-Thursday)
Mahalaya shraddha for those who died in an accident should be performed on Chathurdasi- (September 18-Monday)
For the family member who became a sanyasi and attained siddhii, Mahalaya should be performed on Dwadasi
In general, it is good to do tarpanam every day during Pitru Paksha as it brings peace, prosperity and auspicious events to one’s family and helps the ancestors’ souls rest in peace.