Richard III by William Shakespeare
What you thought: I like to answer with this quote every time somebody asks me for the time. It's sadness time, buddy, now get out of my personal bubble.
But actually: The quote, when read in its entirety, has pretty much the opposite meaning: "Now is the winter of our discontent / Made glorious summer by this sun of York; / And all the clouds that lour'd upon our house / In the deep bosom of the ocean buried." Gloucester, the speaker, is saying that winter is over and life is good, the clouds are gone. What's more, this is partly due to the fact that he is planning to murder his brother, the "sun of York," and usurp the throne. So what this really means is, "Life is rad and I'm going to kill my brother." Hopefully you never need to communicate this sentiment.