Irony is saying the opposite of what you mean — and trusting the obvious gap between your words and reality to signal the joke. Big gap: everyone gets it. Small gap: nobody can tell if you're joking or just wrong. Drag the slider to feel exactly where irony turns into confusion.
“What a beautiful sunny day!” at 1 a.m. can't possibly be a mistake — so it must be deliberate. The obvious gap from reality is the signal that you're joking. Safe to use: everyone will get it.
“It's evening” at 1 a.m. is only a little wrong. Listeners can't tell a joke from an error, so the irony dies — you just seem mistaken. Skip the sarcasm here: you'll only be misheard.
“It's nighttime” matches reality exactly. That's the opposite of irony: a plain, literal, sincere statement. Not a joke, not a mistake — just honest information.