Monday 27th July, 2015: Matatraya Ekadasi, Toli Ekadasi, Sayana Ekadasi, Start of Chathurmasya Vrat
Tuesday 28th July, 2015: Vasudeva Dwadasi
Friday 31st July, 2015: Mahashadi, Vyasa Poornima, Guru Poornima
Adhika masam or Adhik Masa is an additional month that appears in the Hindu Lunar calendar. A year with an Adhika masam will mean that it has 13 months instead of the usual 12 months. The Adhika masam appears only in calendars that consider it. Hence, the local / regional calendars that are followed in Tamil Nadu, Kerala, Orissa, Bengal and Assam will not have them since they follow the Solar Calendar.
Any Solar calendar has 365 days. However, a Lunar calendar will have 354 days. These difference in the days, over years, make up for the additional month upon which there will be a sync between the two calendars. Generally, an adhika masa comes every years (32 months, 16 days and 8 ghadis to be precise). A ghadi is 24 minutes.
Adhika masam is followed by any Hindu regional calendar that follows the Lunar-based calculations. The regional calendars of the states of Andhra Pradesh, Karnataka, Maharashtra and Gujarat will have the lunar month which starts and finishing with the new moon (amavasya day) while the states of North India have their lunar month starting and finishing with a full moon (purnima day).
While the concept of adhika masam is really technical in nature, for the common man, it would mean that there might be slight changes in which celebrations are conducted at the temple. For instance, there might be two brahmotsavams at popular temples, such as that at Tirupati. Tirumala Tirupati Devasthanam for instance celebrates two brahmotsavams during the Adhika Aswayujam. Further, adhika masams are often special prayer time for the devotees of Lord Sri Krishna.
Vikrutinama Samhastra in 2010-2011 during Vaisakamasam
Nandananama Samhastra in 2012-2013 during Bhadrapadamasam
Manmadanama Samhastra in 2015-2016 during Ashadamasam
Vilambhinama Samhastra in 2018-2019 during Jeystamasam
Saarvarinama Samhastra in 2020-2021 during Asweejamasam
Shobhakrutunama Samhastra in 2023-2024 during Sravanamasam
Parabhavanama Samhastra in 2026-2027 during Jeystamasam