Can we talk about the word belated?
Here’s how The American Heritage Dictionary of the English Language (fourth edition) defines it: “Having been delayed; done or sent too late….”
And here’s what The New Shorter Oxford English Dictionary has to say: “Delayed; tardy; coming (too) late.”
So when you’re a dick and you miss someone’s birthday, don’t say, “Happy belated birthday!” The birthday wasn’t late; you were. The correct way to handle the situation, then, is to say, “Belated happy birthday!” And then to not be a dick the next time it comes around.