You and Jesus.
(Did any of the Roman centurions stop and ask “We’re crucifying this guy? Hasn’t his life sucked enough already with his birthday on Christmas day? I mean, there’s no way he gets as many presents that way.”)
Yeah, I refuse to acknowledge the year changing, too. I’m on my 65th 1954 and I’ve saved so much money on champagne and party hats that I can afford a new Thunderbird (at 1954 prices it’s only $2944).
Wrong. Etiquette-wise, it is officially discourteous to give no response to a courteous greeting (unless it’s from a random stranger on the street who has no business addressing you in the first place). Admittedly, silently ignoring an acquaintance politely greeting you is less rude than snarling “Oh shut the fuck up” at them or whatever it is that you’re refraining from saying, but that doesn’t mean it’s not rude.
If you are doing it deliberately to show your disdain for the acquaintance who greeted you, it’s called the “cut direct”. If you are simply failing to respond because you don’t feel like responding, it’s ordinary garden-variety rudeness. As Miss Manners notes,
If you really are such a not-a-morning-person that you absolutely can’t even muster up a nod or halfway-pleasant grunt in response to an acquaintance wishing you “good morning” in passing, the way to avoid being rude is to seek out the acquaintance at some later time of day when you are capable of human communication, and explain to them that you can’t stand even the most minimal human communication in the morning so you hope they won’t take it personally that you’re just ignoring their greetings.
I think it sounds like less trouble just to do the nod or grunt, but that’s up to you. What’s not up to you is whether silently ignoring an acquaintance’s polite greeting is conventionally considered rude behavior. It is, even if you don’t like the fact.