Your contribution must be recharacterized by your tax-filing deadline including extensions. Taxpayers who operate on a Calendar year and file their tax returns by April 15 or file for an extension by April 15 receives an automatic extension of 6-months ( until October 15) to recharacterized their contributions. For instance, if the contribution is for the 2010 tax year, it must be recharacterized by October 15,2011.

If October 15 falls on a weekend or public holiday, the deadline is extended until the next business day. Cite: IRC § 7503

Your recharacterized contribution must include any net income attributable (NIA) to the contribution