The 2015 IRA contribution deadline is in April 2016. As such it is possible to contribute $5500 to my 2015 IRA and $5500 to my 2016 IRA during the 2016 calendar year. My question is simply: if I choose to do this, can I deduct the full $11000 from my 2016 federal income taxes? Or would the 2015 IRA contributions be deducted from my 2015 taxes, and the 2016 IRA contributions from my 2016 taxes?
Context: my income is dramatically higher in 2016 than in 2015 (but I still have no employer retirement plan), so deducting the same amount in 2016 instead of 2015 would be advantageous, if it is possible.