"Los gatos aprendieron inglés hace cuatro años."
Translation:The cats learned English four years ago.
So crazy I know, but my Spanish rehome dog, did actually learn English 6 years ago.
It's the way to say "x time ago". It doesn't translate well into English, although someone might say something like, "I guess that makes 10 years that I've been working here."
I don't think this is something that would be said in English. What would be more likely is to say somebody studied English 4 years ago. To say you learned it is to say there is no more to learn which is not something one would likely say about a language but something more specific like the verb to be or conjugating the future. It's even less likely to say that about cats lol.