अधोलोकवर्णनम् (Adholoka-varṇana) — Description of the Lower Worlds and Cosmographic Measures
निश्चयः सर्वकालस्य युगमित्यभिधीयते / संवत्सरस्तु प्रथमो द्वितीयः परिवत्सरः
niścayaḥ sarvakālasya yugamityabhidhīyate / saṃvatsarastu prathamo dvitīyaḥ parivatsaraḥ
The fixed measure of all time is called a ‘yuga’. Of these, the first is saṃvatsara, and the second is parivatsara.