Skandapurana 16.119.66

16.119.66

varṣārdhaṃ varṣamekaṃ vā siddhāste tattvacāriṇaḥ ..
āśvayukchuklapakṣe ca manvādiṣvaṣṭakāsu ca .. 66 ..

for half a year or for one year, become perfected practitioners who move in the truth. / And in the bright fortnight of the month of Āśvina, at the beginnings of the Manvantaras, and on the Aṣṭakā days,