Brahmandapurana 2.74.232

Brahmāṇḍapurāṇa 2.74.232

saptarṣīṇāṃ yugaṃ tvetaddivyayā saṃkhyayā smṛtam /
māsā divyāḥ smṛtāḥ ṣaṭca divyābdāścaiva sapta hi //