Today, 11 September 2012 is Ekadasi. Smarta people observe today as Ekadasi vrat. Vaishnava sect of devotees observe 12 September as Ekadashi vrata (Bhagvat Ekadasi). It is known as Parama Ekadasi (Kamla Ekadasi / Purushottam Ekadashi).
It falls in Krishna Paksha of Adhika Bhadrapad Month as per Telugu, Kannada, Gujarati & Marathi calendars; in Nija Bhadrapada Maasa in North Indian Hindi Panchangams.
Ekadasi of September 11/12 falls in Avani Masam in Tamil calendar, Chinga Masam in Malayalam calendar and Bhadra Month in Bengali calendar.