There are three different decision by various vidwan about Sama Upakarma of this Sri Nandana Year!
1. Most of the Vaakya Panchangams : 24th July 2012 stating the reason
Avani - Mala Maasam
Purattasi - Maadhappirppu ( Sankraman dhosham)
so preponned to Aadi i.e 24th July.

2. Srirangam Panchangam and some Drik Kanitha panchangams:
17th September 2012
stating, though there is dhosham, the Nija bhatrapada month should be taken to account.

Dear you, Thanks for Visiting Brahmins Net!
JaiHind! Feel free to post whatever you think useful, legal or humer! Click here to Invite Friends

3. By Sama Bruhaspathi Venugopalan Chennai.
His statement and explanation given as pdf below:

Below the video of the sathas done for it: