अग्निनिचयः (Agninichaya) / The Accumulation of Sacred Fire & the Classification of Pitṛs by Time-Order
तपाश्चैव तपस्यश्च मन्युमन्तौ तु शैशिरौ / कालावस्थासु षट्स्वेते मासाख्या वै व्यवस्थिताः
tapāścaiva tapasyaśca manyumantau tu śaiśirau / kālāvasthāsu ṣaṭsvete māsākhyā vai vyavasthitāḥ
Tapa and Tapasya, and also Manyumanta and Śaiśira—these six names of months are duly set within the six conditions of Time.