So?? What’s the big deal? Your friends love you so much that they threw you a party!! Just because they were off by one day doesn’t change that! Honestly, did it occur to you that they maybe couldn’t have the party on your birthday for other reasons? Or that they might have been trying to “throw you off the scent” so you wouldn’t guess what they were planning? You don’t sound very grateful to me.

You sound like a spoiled brat. A spoiled, ungrateful brat. Honestly, what a stupid thing to be upset about!

I’ve normally thrown surprise birthday parties on days that are not their actual birthday. It makes for a better surprise because the recipient is really not expecting it. Why would you just assume that they don’t know your birthday? And instead of being ungrateful and complaining on the internet, why wouldn’t you just ASK your friends why they had it the day prior? You sound extremely narcissistic. I’m amazed anyone would want to go through the trouble of throwing you a surprise party.

maybe that's how they made it a surprise

they know when your birthday was. it wouldn't have been as much of a surprise on your birthday. they didn't every single one collectively think it was the same wrong date you're really ungrateful