Like, forever?
We’ve done this many times before: while everyone with a basic understanding of the sun/earth/moon configuration knows that the far side of the moon gets about as much light as the close side (excepting the occasional lunar eclipse), the expression “the dark side of the moon” has long been understood to mean the far side.
And one doesn’t have to read “dark” literally. The word is often used to mean something hidden or obscured, as in the (old fashioned and slightly racist) phrase “darkest Africa,” which obviously didn’t mean literally dark, but largely unexplored (by white people).
A recent thread on the subject.