The Census API provides ACS 5 data for 2011 and 2012 (along with more recent years).
The Census's TIGERweb services provides census tract geometries for the 2013 ACS release and the 2010 Decennial Census.
Are the census tracts used in the 2011 ACS and 2012 ACS the same as either the 2010 or 2013 geometries? If not, is there a web service that provides the 2011 and 2012 geometries?