Saptami Shraddha could be performed for those souls who have departed on Saptami Tithi.
Deceased may be died in any Paksha or Lunar Fortnights i.e. Shukla Paksha (Bright Fortnight)
or Krishna Paksha (Dark Fortnight).
Read More : Cost of Pind Daan/ Asthi Visarjan/ Nagbali/ Narayan Bali/ Tripandi etc.
Pitri Paksha Shraddha are Parvan Shraddhas(पार्वणश्राद्ध) and auspicious time to perform them is either Kutup Muhurt or Rohina Muhurt .
It could be performed till Aparahna Kala (Post Meridian) gets over.
Tarpan (तर्पण) could be performed at the end of the Shraddha.