Sales (and buys) are reported (IRS tax form, Sched. D) on TRADE DATE, not on the date when the sale/buy closes. So if you press the sell button for a stock in your account on the last day the market is open in 2005, you got to report that on April '06. (Sell shorts though remain open until they are closed.)
Geez man, how long you been buying and selling stocks, and how long have you been wrong?