How is the meaning of "once upon a time" different from "a long time ago"?
Literally, is that what it means? There seems to be repetition in once and upon a time. How is this sentence broken up?
According to OED, once upon a time means at some time in the past (used as a conventional opening of a story). or formerly.
On the other hand, a long time ago means a long time ago in the past. Now, they could be used interchangeably in some cases, but once upon time could refer to something that happened a few days or a month ago, which is not long time ago, while the other couldn't.
Once upon a time there was a little girl who loved discussing things over an Internet forum.
It wasn't a long time ago. A long time ago there were no Internet forums.