Adhika masa or Adhik month in 2015 is Adhik Ashada masa. It is an extra month for those who follow Chandramana Panchangam or lunar calendar. In 2015, Adhika masa Ekadashi are known as Padmini Ekadashi (Kamala Ekadasi) and Parama Ekadasi (Kamala Ekadashi).
Here are the Ekadashi dates in Adhika masa 2015 as per North Indian Hindi calendar
Kamala Ekadashi (Yogini Ekadashi) – 12 June 2015
Kamala Ekadashi – 28 June 2015
Adhika Masa Ekadashi dates as per Amavasyant Panchang followed in Marathi, Gujarati, Telugu, Kannada & Konkani calendars…
Kamala Ekadashi – 28 June 2015
Kamala Ekadashi – 12 July 2015
It is to note that Smarta sect of people observes Ekadashi vrat and fasting during the day it begins and Vaishnava sect of people observe the vrat when it ends. These Ekadashi dates are given as per Telugu, Kannada, Marathi, and Gujarati calendars and North Indian Hindi calendars.