अधोलोकवर्णनम् (Adholoka-varṇana) — Description of the Lower Worlds and Cosmographic Measures
त्रिशदेव त्वहोरात्रास्तैस्तु मासस्तु भास्करः / एकषष्टि त्वहोरात्रमृतुरेको विभाव्यते
triśadeva tvahorātrāstaistu māsastu bhāskaraḥ / ekaṣaṣṭi tvahorātramṛtureko vibhāvyate
Thirty days and nights are reckoned as one month of the Sun (Bhāskara); sixty-one days and nights are understood as one season (ṛtu).