When is sankrAnti celebrated? If the sun lies in dhanuSh-rAshi at sunrise and only crosses over to makara afternoon (as is the case in 2018 relative to India time), is sankrAnti celebrated on that day itself or on the following day? What are the pramANa-s?
It's been rather tricky this time :). In general, we perform puja in Uttarayanam. As long as the sun transits over before sunset, the puja is done on the same day. This time, according to Srirangam Vakya Panchanga, it's approx. 17:05 IST (Drik Panchanga: 13:50 IST). We're doing the puja at ~3 pm IST, so that the puja will be over before Pradosha time (It's Pradosha day as well!). Whenever there are such complexities, it's just convenient to follow whatever the Purohit says!
Happy Sankranti! नमः सवित्रे जगदेकचक्षुषे!