According to Merriam Webster – any time you want.
Like many other people, I’ve been frustrated by the apparently incorrect use of the word literally. It turns out, that I was wrong.
According to Merriam Webster, the hyperbolic use of the word for effect has been in use as far back as 1769. In literature, it has been used by Charles Dickins, F. Scott Fitzgerald, James Joyce, and many others.
This surprising fact has literally blown my mind!
literally \ ˈli-tə-rə-lē \
2: in effect : VIRTUALLY — used in an exaggerated way to emphasize a statement or description that is not literally true or possibleLiterally | Definition of Literally by Merriam-Webster
Incidentally, it’s not just Merriam Webster that features this definition. The Oxford English Dictionary does as well, among others.