Amāvasyā-Pitṛtarpaṇa: Purūravas and the Soma-Based Ancestral Offering (अमावस्या-पितृतर्पण / सोमतर्पण-विधि)
ऋतवः पितामहा मासा अयनाह्यब्दसूनवः / प्रपितामहास्तु वै देवाः पञ्चाब्दा ब्रह्मणः सुताः
ṛtavaḥ pitāmahā māsā ayanāhyabdasūnavaḥ / prapitāmahāstu vai devāḥ pañcābdā brahmaṇaḥ sutāḥ
The seasons are the pitāmahas (grandfathers); the months and the ayanas are sons of the year; and the gods as prapitāmahas (great-grandfathers) are called Pañcābda, sons of Brahmā.