Skandapurana 16.273.10

16.273.10

bhavecca tasya tṛptistu yāvatkalpāstu saptatiḥ ..
māsa āśvayuje devi kṛṣṇapakṣe caturdaśī ..
tatra dadyāttu yaḥ śrāddhaṃ dakṣiṇāmūrtimāśritaḥ .. 7.1.273.10 ..

and their gratification shall last for as long as seventy kalpas. / In the month of Āśvayuja, O goddess, on the fourteenth day of the dark fortnight, / whoever gives a śrāddha there, having taken refuge in Dakṣiṇāmūrti,