It's three days late this year due to the weekend, but it's today.
So this is your friendly reminder to please not be stupid and claim that the 16th Amendment is illegal or that it was never ratified or that Ohio wasn't actually a state until 1953 and so their ratification doesn't count or whatever other fit of idiot libertarianism you come up with that equals "hey, I don't have to pay taxes!" Someone tries it every year, and every year it just ends in that someone's arrest and a cheap laugh for the rest of us. It is regarded as so utterly ridiculous that legally, it is classified as a frivolous argument, which means not only 'you're an idiot; get out of my courtroom', but, due to Rule 11 of the Federal Rules for Civil Procedure, it also means 'the law firm that took your so-called "case" is an idiot too for making me put up with you, and I'm going to punish them for making me have to listen to your crazy'.
Also, you should note that, under section 7482 of the tax code, "The United States Court of Appeals and the Supreme Court shall have the power to require the taxpayer to pay to the United States a penalty in any case where the decision of the Tax Court is affirmed and it appears that the appeal was instituted or maintained primarily for delay or that the taxpayer’s position in the appeal is frivolous or groundless," and frivolous arguments in United States Tax Court, under 26 U.S.C. § 6673(a)(1), could result in up to a $25,000 penalty.
How counter-productive of you.