Never put off till tomorrow what you can do day after tomorrow just as well.

Mark Twain (1835-1910) American writer [pseud. of Samuel Clemens]
“Memoranda: The Late Benjamin Franklin,” epigraph, The Galaxy Magazine (Jul 1870)
    (Source)

Offered as a faux Franklin maxim, in an essay where Twain mocked veneration of Franklin's biography and supposedly original aphorisms.

More background on this quotation: Never Put Off Till Tomorrow What You Can Do The Day After Tomorrow Just As Well – Quote Investigator.