अग्निनिचयः (Agninichaya) / The Accumulation of Sacred Fire & the Classification of Pitṛs by Time-Order
दिवसार्द्धमासमासैश्च ऋतुभिस्त्वयनैस्तथा / संवत्सरस्तु प्रथमो द्वितीयः परिवत्सरः
divasārddhamāsamāsaiśca ṛtubhistvayanaistathā / saṃvatsarastu prathamo dvitīyaḥ parivatsaraḥ
In the sequence of day, half-day, month and sub-month, seasons (ṛtu) and ayanas— the first is called Saṃvatsara, and the second Parivatsara.