Bharani Shraddha is done during Pitru Paksha when Bharani Nakshatra prevails during Aparahna Kala. Bharani Nakshatra prevails either on Chaturthi Tithi or Panchami Tithi during Mahalaya Paksha.
Bharani Shraddha is known as Chauth Bharani or Bharani Panchami when Bharani Nakshatra prevails during Aparahna on Chaturthi Tithi or on Panchami Tithi respectively. (In some years Bharani Nakshatra might also prevail on Tritiya Tithi. Hence Bharani Shraddha is not linked to any Tithi.)
Bharani Shraddha is known as Maha Bharani Shraddha. Nakshatra Bharani is significant during Pitru Paksha because it is ruled by Yama, the God of the Death.