When the Sun enters a new rasi, a Tamil solar month begins (sankraman). Auspicious punyakalam windows around that instant differ by sign type: Vishnupathi (fixed / Vishnu), Shadasheethi (dual / Shiva), Vishu (movable equinoxes / Brahma), and the ayanas (movable solstices / Shiva). Choose a year and location to see local month-start times and each punyakalam start–end window.