Kāla-vibhāga: The Divisions of Time from Atom to Brahmā, and the Lord Beyond Time
अयने चाहनी प्राहुर्वत्सरो द्वादश स्मृत: । संवत्सरशतं नृणां परमायुर्निरूपितम् ॥ १२ ॥
ayane cāhanī prāhur vatsaro dvādaśa smṛtaḥ saṁvatsara-śataṁ nṝṇāṁ paramāyur nirūpitam
A day and night of the devas are said to be made of two ayanas; that combined day and night is, for human beings, one complete year (saṁvatsara). The highest span of human life is fixed as one hundred years.
This verse states that two ayanas constitute a day and night for the devas, twelve months form one year, and the maximum human lifespan is described as one hundred years.
In Canto 3, Chapter 11, Śukadeva explains the structure of time to show its vast, ordered nature and to help the listener cultivate detachment and urgency for spiritual realization.
Remembering life’s limited span encourages disciplined sādhana, wiser priorities, and reduced attachment to temporary achievements.