The IRS delayed the federal income tax deadline in observance of a Washington, D.C. holiday - Emancipation Day - on Monday, April 16th. The traditional deadline of April 15th had already been extended one day because April 15th is a Sunday.The Ohio Department of Taxation (ODT) has extended the Ohio income tax filing deadline to April 17th in order to bring Ohio in line with an IRS extension of the federal income tax deadline.