Early Voting - can it be taken back?

Anyone else notice how the standard argument to just about anything that happens concerning the U.S. government that someone doesn't like is:

"I don't like __________, and by the way it's unconstitutional!"

When there is absolutely nothing in the Constitution about __________?

Voting dates are determined by the states, not the federal government. Election Day is set by the federal government in 2 USC 7 as:

"The Tuesday next after the 1st Monday in November, in every even numbered year, is established as the day for the election, in each of the States and Territories of the United States, of Representatives and Delegates to the Congress commencing on the 3d day of January next thereafter."

Election Day is when all votes are counted. I'm surprised someone hasn't said that mail in absentee ballots are unconstitutional because they have to be filled out before Election Day.