Mark Twain's birth and death both happened on days in which Haley's Comet could be seen.

What's interesting is that he even foretold of this happening, quoted as saying, "I came in with Halley's Comet in 1835. It is coming again next year, and I expect to go out with it." Sure enough, the next year, he died of a heart attack on April 21, 1910, when the comet was visible.

Halley's comet has been observed for centuries now. Its first appearance was recorded as early as the 200s BC. It is visible from Earth around every 75 years. It was last seen in February 1986, so the next predicted date for it to be visible is July 2061.

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