If you're one of the hundreds of thousands of taxpayers who wait until the last minute to file your taxes, make a note: The IRS has just announced that the due date for 2010 individual federal income tax returns will be Monday, April 18, 2011.

Traditionally, Tax Day falls on April 15 unless that day happens to be on a Saturday, Sunday or federal holiday. In 2011, April 15 meets none of those criteria -- it falls on a Friday, and there's no federal holiday that day.

So what's the deal? In 2011, Washington, D.C., will celebrate Emancipation Day on April 15, a day earlier than normal, since April 16 falls on a Saturday. Emancipation Day marks the anniversary of the day that President Lincoln signed the Compensated Emancipation Act. The Act, which was "for the release of certain persons held to service or labor in the District of Columbia," freed 3,100 slaves in the District, making DC residents the "first freed" by the federal government. In 2005, Emancipation Day was made an official public holiday in the District of Columbia.

In observance of the DC holiday, Tax Day will be moved forward one business day, this year landing it on Monday, April 18. That's the date your form has to be either submitted electronically or postmarked by for your tax return to be considered timely filed by the IRS.

Don't be fooled into believing that the day moves all individual federal income tax deadlines forward. The overseas exception due date will still be June 15, 2011. However, individual federal income tax returns on a "normal" extension will be due on Monday, Oct.17, 2011; that's because Oct. 15, 2011, (the regular extension due date) falls on a Saturday.