When the 16th Amendment was ratified on Feb. 3, 1913, it allowed Congress to institute an income tax. Congress picked March 1 as the deadline for filing returns, and the first official tax day was March 1, 1914.
A few years later, Congress passed the Revenue Act of 1918, raising income tax rates and moving the filing date to March 15. The new date remained unchanged for nearly 40 years.
In 1955, the date was moved forward again. The Internal Revenue Service stated that the later date of April 15th helped government employees to spread out the heavy workload. But some economists speculate that a later filing date means the government can wait even longer to pay refunds. Of course, the longer the IRS can hold onto the money it withholds via payroll taxes, the more interest that money earns.
But even the April 15 due date can shift a little. In 2005, the District of Columbia enacted Emancipation Day on April 16 to commemorate the day Lincoln signed an 1862 law freeing the first slaves in Washington, D.C. So when April 16 falls on a Saturday, the holiday is officially celebrated on Friday, and when it falls on Sunday, it’s celebrated on Monday.
That’s why this year the tax deadline is Monday, April 18. Federal and state governments have also moved back deadline dates from time to time to accommodate people affected by regional natural disasters, such as huge snowstorms.