In 2011, I made a large charitable contribution to my school. Some is still left over, despite my having taken the maximum allowable charitable deduction each year. I know that I cannot carryforward this deduction beyond 2016.
My question is: do I have to file my 2016 return by April 15, 2017 to take a deduction for the 2011 contribution, or do I have until Oct 15, 2017 (after filing for an extension)? (I am trying to plan a trip which, if I take it, will necessitate filing for an extension.)