Incorrectly attributed to Twain, this is actually a quotation from an article in The Pocono Record (18 February 1971, page 4 http://www.newspapers.com/newspage/40447792/)
Misattributed
Mark Twain: Quotes about time (page 3)
Mark Twain was American author and humorist. Explore interesting quotes on time.Source: Mark Twain's Notebook (1935), p. 393
Czar Nicholas II
1905
Collected Tales, Sketches, Speeches, & Essays, 1891-1910 (1992) ed. Louis J. Budd
Source: Adventures of Huckleberry Finn (1885), Ch. 18
Source: The Adventures of Tom Sawyer (1876), Ch. 35
Source: Autobiography of Mark Twain, Vol. 2 (2013), p. 475
Ch. 22 http://www.literature.org/authors/twain-mark/connecticut/chapter-22.html
A Connecticut Yankee in King Arthur's Court (1889)
“No accident ever comes late; it always arrives precisely on time.”
Source: Autobiography of Mark Twain, Vol. 2 (2013), p. 239
Letters from the Earth (1909)
Source: Adventures of Huckleberry Finn (1885), Ch. 16
Concerning the Jews (Harper's Magazine, Sept. 1899)