Dispute it

Always write important dates down

Well you both are pretty ******* stupid

Show them your reservation/receipt. If it's an error on their part, they have to at the very least reimburse you! Don't go down without a fight!

I've been working in hotels for over a decade as a night auditor. I couldn't even guess how many times I've had to turn away walk-ins because the only vacant rooms were reserved for people that never showed up. I don't feel bad about charging those no-shows because the vacant rooms could have been easily occupied otherwise. If you want the privilege of having a room guaranteed for you then you have to pay the consequences of a no-show. And if you made the reservation online, whether directly through the hotel's website or through a third party like priceline.com or hotels.com then it's your own damn fault for choosing the wrong date. The only way this would have been the hotel's fault is if they overbooked (usually a rarity these days) for the day you scheduled your reservation or if you called it into the hotel directly and they entered the wrong date (also relatively uncommon although it does happen). This is definitely, absolutely, with out a single shred of doubt a YFDI.

who's mistake? bet it's the hotel's lol

Reminds me of an episode of friends