Sani Trayodasi or Shani Trayodashi is an auspicious day for Shani Puja. In April 2011 it falls twice – April 16 and April 30. Sani Trayodasi is observed on 13th day in a fortnight which falls on Sanivar (Saturday). Sani Thailabhishekam, Shani Shanti puja, and Shani homam are the best rituals to perform on this day to pacify the bad effects of Shani.
Sani Trayodasi on April 16, 2011 – It falls in Shukla Paksha in Chaitra month.
Sani Trayodashi on April 30, 2011 – It falls in Krishna Paksha in Vaishakh month / Chaitra month.
Next Shani Trayodasi will be in August 2011.