Time flies like an arrow

After installing the latest Babylon version 6, I couldn't resist testing the NLP-famous-example-sentence I've learned from my best friend's father, a computer expert, some 15 years ago... time flies like an arrow. Does it mean, "time flies" like an arrow? or does it mean, time (as in space-time) flies like an arrow? Or does it mean, time (as a verb) flies like an arrow? You can't know, out of context, what the sentence is supposed to mean, hence the trouble for Natural Language Processing programs. Babylon chose the latter...