Pitṛ Pakṣa

Pitṛ Pakṣa is the fortnight of the ancestors: the dark half of the lunar month after the Bhādrapada full moon, usually in September–October. Each family does śrāddha on the tithi matching the ancestor's death.

It ends on Sarvapitṛ Amāvasyā (Mahālaya Amāvasyā), when anyone whose date is unknown, or who was forgotten, is remembered together. Many families avoid starting major celebrations in this fortnight, but it is a time of remembrance, not of bad luck.

About Sept–Oct · Ends on Mahālaya Amāvasyā

Karmakāṇḍa — the ritual way · Ask a Jyotishi your own question