Sani Mahapradosham - If it falls on Saturday and earlier day of Mahasivarathri
http://en.wikipedia.org/wiki/Pradosha#Shani_Pradosha
http://www.astroved.com/pradosham/
http://www.drikpanchang.com/vrats/pradoshdates.html
https://www.youtube.com/results?search_query=Sani+Pradosham
