Vaishnava Dharmashastra 73.8

73.8

āgrahāyaṇyā ūrdhvaṃ kṛṣṇāṣṭakāsu ca krameṇaiva prathamamadhyamottamapañcakaiḥ ||

On the Ashtakâs (or eighth days) of the (three) dark halves subsequent to the full moon day of the month Âgrahâyana (or Mârgasîrsha), during the recitation of the first, second, and last Pañkakas respectively;