Narapatijayacarya 3.1.3.33

3.1.3.33

ṛtau rāśyaṃśako grāhma ṣaṇmāse dhiṣṇya saṃbhavaḥ ||
abde piṇḍasvaro jñeyo yoge dvādaśavārṣike ||

in a season, the sign division is to be taken; in a half-year, that which arises from the lunar mansion;
in a year, the aggregate-sound is to be known, in the twelve-year cycle.