Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 51.7

51.7

manvantarādayaścaite anantaphaladāḥ smṛtāḥ /
ayane cottare rājandakṣiṇe śrāddhamācaret //

these are the beginnings of the manvantaras, remembered as giving endless fruit. / On the northern solstice, O king, and on the southern, one should perform a śrāddha;