Skandapurana 6.3.51.5

6.3.51.5

āṣāḍhasyaiva daśamī māghasyaiva tu saptamī .
śrāvaṇasyāṣṭamī kṛṣṇā tathāṣāḍhasya pūrṇimā .. 51.5 ..

the tenth of Āṣāḍha, and the seventh of Māgha; / the dark eighth of Śrāvaṇa, and the full moon of Āṣāḍha;