Amendment to section 80I narrows qualifying period, shortens specified term and revises a statutory year reference. Amendments to section 80I insert a transitional cutoff limiting eligibility to a period after an initial commencement date but before a later cutoff (also added in a proviso), reduce the duration referenced in specified clauses from a longer term to a shorter term, and substitute an earlier statutory year reference, thereby narrowing the temporal scope and duration of the section's incentives.