Sir,
Before issue of Notification No. 6/2015-CE (NT) dated 1.3.2012 the third proviso to rule 4(1) of CENVAT Credit Rules, 2004 read as "Provided also that the manufacturer or the provider of output service shall not take CENVAT credit after six months of the date of issue of any of the documents specified in sub- rule (1) of rule 9.
Now the above referred Notification substitute the word " six months" by the word "one year". This Notification comes into effect on 1.3.2015. Therefore on 1.3.2015 if the invoice date is within one year, that is, invoice was issued on or after 1.3.2014 then you can take credit. Even in respect of invoices which you had not taken credit due to old proviso now if the date of such invoices are on or after 1.3.2014 now you can avail the credit. This is my opinion.