This year the deadline for filing various tax returns normally due on April 15 is being changed to April 18, 2011. The reason? Washington, D.C. is observing its Emancipation Day holiday on Friday, April 15, and though that’s not a national holiday, the Treasury Department has extended Tax Day 2011 to Monday, April 18. The new deadline applies to individual and partnership tax returns, extension requests, and other tax deadlines such as making 2010 IRA and education savings account contributions and making the first 2011 estimated tax payment.