Due date for e-filing service tax revised return

Hi Members !! i just wanted to know about the due date for e-filing of revised service tax return. Since, with the recent amendments, due date for e-filing returns was extended upto 26.12.2011, but if a taxpayer has e-filed his return on say, 15.12.2011 and now he wants to revise then upto which date can he e-file revised return ? Please help !!!