If you’re wondering why, visit the IRS website:
Excerpt: “… Taxpayers will have until Monday, April 18 to file their 2010 tax returns and pay any tax due because Emancipation Day, a holiday observed in the District of Columbia, falls this year on Friday, April 15. By law, District of Columbia holidays impact tax deadlines in the same way that federal holidays do; therefore, all taxpayers will have three extra days to file this year. Taxpayers requesting an extension will have until Oct. 17 to file their 2010 tax returns….”
For more about the law that governs tax deadlines, see the March 7th, 2011, IRS Bulletin 2011-10.