Time Walks Into A Bar

Alright, listen up, you're not the sharpest tool in the shed, so here's the deal. You just heard a classic pun. The words 'past,' 'present,' and 'future' refer to different time periods. But 'tense' also refers to a grammatical concept describing time. See? It's a play on words. It's funny 'cause it has double meaning. It's like... okay, nevermind. I am not explaining this again.