There are many Hindu scriptures that describe the importance of performing Shradh ceremonies of ancestors. The period of sixteen days starting from the Purnima of the Bhadrapada month until the day of Amavasya which usually falls during the month of August-September is known as Pitru Paksha. Irrespective of the month or paksha, one can perform Shradh and offer Tarpan during the Pitru Paksha. It is believed that ancestors from the Pitru Lok visit earth and receive the offerings made by the family members in the form of Shradh and Tarpan and bless the lineage a happy and prosperous life.
Dwadashi Shradh
Dwadashi is the twelfth day of the lunar month and shradh performed of those family members who died on the Dwadashi tithi. This day is also meant for performing Shradh of those who breathe their last after taking the renunciation. The other name of Dwadashi shradh is Baras shradh. Since Trayodashi usually falls on the same day, some people perform the Trayodashi (thirteenth day of the lunar month) shradh on the same day. This year, Dwadashi Shradh falls on 25th September 2019.
The significance of performing Shradh in the favorable Pitru Paksha
Hinduism strongly believes in the concept of life after death. In order to please the ancestors who stay in the ancestral world, ceremonies like Shradh and Tarpan are offered. It is believed that ancestors eagerly wait for their family members to offer Tarpan and quench their hunger and thirst. That is why one must perform Shradh rituals with a lot of faith and sanctity.