Tax Day Monday? or is it Tuesday?

Today is tax day. At least I think it is. No one seems to be mentioning the fact that it might be tomorrow. What holiday, Federal holiday that is, is it that's changing things this year? No one seems to know that either. The IRS web page doesn't say anything specifically about today or tomorrow, nor does the book. The only place I may have found some mention of a date was my State's web page, but even then, there was no reason as to why it was tomorrow not today.
I got mine done today, just because I don't know. Monday or Tuesday?
I think it would be easier for the Federal Government to just go to a nationwide sales tax. Why not? It would allow, in a backhand sort of way, to make those who do not go through the agony of filing a tax return pay some sort of tax. I mean those illegals, drug dealers, and other "unspecified" non-tax filing Americans.
That in itself opens up a whole other ball of conflict, one that I will not delve into today. Let's just hope that all who were supposed to file were able to and for those who didn't, don't or choose not to, I hope you have a nice day.