Why April 18th?
April 15 is a Saturday. The tax deadline always gets postponed when it lands on a weekend or a legal holiday. Tax Day would typically shift to Monday, April 17. But …
April 16 is Emancipation Day, a Federal holiday marking when President Abraham Lincoln freed slaves in 1862. When it falls on the weekend, it’s celebrated on the following Monday. But …
April 18 is the deadline for filing 1040s and such. Or to apply for an extension.