Warning: while this post may be about comedy, don’t expect it to be comic.
I would consider the quote “comedy is tragedy plus time” an old saw, but it’s still an interesting idea. Could every tragedy become funny, given enough time? The British comedian David Mitchell seems to think so. (His video rant, which tries to explain why Vikings raping and pillaging in the Dark Ages is funny, but the Soviet takeover of Berlin in 1945 isn’t yet, is embedded below.)
The quote should really be, tragedy plus time allows comedy. Depending on how you portray events, you can still achieve either a laugh or tears, and sometimes both. That’s what art is all about, right? But can you imagine taking a scene say, Schindler’s List, and turning that into a rip-roaring farce? Wait, no! Don’t even try to imagine it, because, as they say in another cliché: “it’s too soon. ” You can make jokes about Nazis (not much fun in Stalingrad), but please, no jokes about their atrocities. Personally, genocide strikes me as one of those events that is impossible to turn into comedy, no matter how long ago it happened. (But perhaps I’m not really trying. Maybe there is some good humor to be had in the Church’s elimination of the Cathars, for example.)
Proto-goth and journeyman of the bon mot, Horace Walpole once wrote to a friend, “The world is a tragedy to those who feel, but a comedy to those who think.”
I think I like that quote even more, because it gets to the heart of the difference between the two. Of course, it may be that I remember the quote: “Comedy is tragedy plus time” as coming out of the pie-hole of Alan Alda’s character (the abrasive Lester) in Crimes and Misdemeanors, and not from Carol Burnett, as the Wikiquote would have us believe. (Crimes & Misdemeanors was a 1989 Woody Allen film, and Burnett’s quote is attributed in 2004 in Wikiquote. I’ll let wiser heads sort the provenance out.)
I definitely don’t agree with Lenny Bruce, who said: “Satire is tragedy plus time. You give it enough time, the public, the reviewers will allow you to satirize it. Which is rather ridiculous, when you think about it.” The beauty of satire is that you can go for it right away. It might not get any laughs if it’s too early though.
Of course, none of these sharp observations are as funny as Mel Brook’s 2000-Year-Old Man (1961): “Tragedy is when I cut my finger. Comedy is when you fall into an open sewer and die.”
If you’re still looking for help on this one, you may find the tragedy-to-comedy conversion chart useful:

(via Comics vs Audience)
Now, as promised, here’s Mitchell on why the Vikings aren’t funny. I do agree with him on one thing for sure: the Vikings didn’t wear horns on the helmets.
Sir Thomas More presents “The Religions of Utopia” (circa 1515) –> slide three
As he watched the proceedings unfold in court, Dr. Maximillian Tundra was starting to understand how Mohammed or Jesus might feel if they could see what had happened to their teachings.
The Odyssey is a story about a homicidal maniac (Odysseus) who refuses to ask for directions. This tragic flaw, shared by many men, leads his crew to disaster. Some are eaten by monsters, some are eaten by their crew-mates, and some finally get fed up with this cruise from hell (literally at one point), and take a flight back to Greece on their own.
This is another tale of vacations gone awry. Bilbo Baggins is a wealthy hobbit who hires Gandalf Travel to take him on a grand tour of Middle Earth.
I read this originally in French class, sometime during my storied high school career. Most of this famous existential work was read aloud in class, by a collection of students with a wide variety of accents and grasp of the French language. If I remember correctly, Lorne’s delivery was hilarious, but that might have been because he was pretending he was Soupy the Clown.