As a warning, since it isn't something I normally do, this story does involve hyper-messing. I tried not to be too graphic or gross about it, but it is there, so if that's not something you're into, then beware!

The invitation had definitely been a mistake, but Sierra wasn't going to let that stop her. She'd had her suspicions ever since she'd gotten it, since it didn't list a name saying who it was meant for, just her address, and, after looking up the return address, she'd seen it was in the rich neighborhood.

Why not, though? A nice, fancy party would be a nice way to ring in the new year! Thanks to that stupid Santa, she'd spent quite a few of her most recent Christmases diapered, if not totally regressed, and tucked into bed far before midnight. This year, by some miracle, she'd avoided that, and it would be a waste not to get to enjoy it.

The house was even bigger than she'd imagined, and, even in the nice, sparkly dress she'd bought for the occassion, she felt out of place as she shuffled up to the door, holding out her invitation and hoping she wasn't turned away immediately, since the ride she'd gotten was already on its way out.

Instead, she was let right in, and right away started to look for the servers to get some hor d'oeuvres to snack on as she listened in to conversations, trying to nod along and act like she understood anything about investments, or running a business, or at least like she wasn't completely lost. It didn't do much to make her feel like a grown-up, or like she belonged here, but at least the food was yummy.

And then she saw the champagne flutes. It was still relatively early in the night, and she had no doubt that a server would be by right before midnight, but she went ahead and grabbed one anyway. Part of her wanted to taste it right away, since she'd never had any before, but just holding it made her feel more confident, and more mature, and she decided it would be more special if her first sip came at midnight.

She chuckled along at jokes, giving her glass a swirl, and only spilling a bit of the contents once or twice before figuring out the best way to do it, very pleased with herself, and the way the end of this year was going, after how rough it had been in general.

And then a hand clamped onto her shoulder. "Excuse me," a much taller woman stared down at her, her fancy dress making Sierra's look pitiful in comparison. "What are you doing up this late, young lady? And why do you have this?"

"Hey!" Sierra whined as her champagne was taken away.

"That isn't for little girls!" the woman scolded.

"Well, I'm not a little girl!" Sierra exclaimed.

The woman raised an eyebrow, Sierra blushing and squirming, certainly feeling like one now, in front of her. "You aren't one of Bethany's little friends? I could have sworn I recognized you from her birthday party."

"I-I don't even know who Bethany is!" Sierra told her, glad this was cleared up, reaching for the champagne flute again.

The woman easily lifted it out of her reach. "No, I'm positive that was you," she shook her head. "I know how to clear this up. Nanny!"

"No!" Sierra groaned, not liking where this was going. "I don't need a nanny! I'm an adult!"

"We'll see about that," the woman said, as another woman stepped over. Her dress wasn't quite as nice as the first woman's, but she was a bit taller, and looked far stricter. Sierra found herself standing up a little taller, just seeing her. "This is one of Bethany's friends, isn't it?"

"Hmm," the Nanny eyed Sierra up and down. "No, I don't believe so."

"See?" Sierra let out a sigh of relief. "I told you!"

"She's clearly underage, though," the Nanny continued. "Because she's had an accident."

"Wh-What?!" Sierra blushed, looking down at herself just to ensure she didn't see anything, which probably didn't help her sound confident as she insisted. "N-No, I didn't! Look!"

She was so used to being kept in diapers, and training pants, and wearing outfits that were designed to make checks and changes easy, she automatically reached for the hem of her dress. In a way, she was grateful the Nanny stopped her.

"You are in public, young lady," she was reminded. "And there's no need for it, anyway. A Nanny always knows," she sniffed. "I can tell your undies are wet. Come along. I suppose a Nanny's work is never done."

"No!" Sierra whined as the Nanny took her hand, pulling her free from the first woman's grip, dragging her through the party. Sierra blushed, hoping that nobody else had overheard the conversation, and knew why she was being pulled away, down a dark hallway and into what seemed to be a guest bedroom, where she was immediately pulled over the Nanny's lap.

"Staying up past your bedtime, trying to sneak alcohol, wetting yourself and lying about it," the Nanny shook her head. "You're in for quite the spanking, little lady."

"B-But that isn't true!" Sierra insisted. "None of it!" That didn't stop the Nanny from giving her a hard swat across the squirming backside, however. Sierra yelped, kicking her feet helplessly, held firmly in place as the woman warmed her bottom thoroughly, until, at last, it was too much for the poor little witch.

Only then, as if she was right about Nannies always knowing, and had been waiting for it, did the Nanny lift the back of Sierra's dress, exposing her underwear. "Not true?" she asked, staring down at the fresh damp patch. "That looks like an accident to me."

"I-It's because of the spanking!" Sierra sniffled. "I-It just happened!"

"You've already proven yourself to be a liar," the Nanny said, "So why should I trust you? Into the corner with you, naughty girl."

Sierra was lifted off the woman's lap, pushed into the corner of the room, the back of her dress tucked into the waistband of her soggy panties. "I'm going to go get a diaper from one of Bethany's dolls," the Nanny informed her. "And you are not going to move a muscle while I'm gone, or we'll start that spanking up from the beginning again before I tape you into it."

"D-Diaper?!" Sierra gasped, fidgeting anxiously at the sound of the word. Suddenly, she had a feeling that invitation hadn't been a mistake after all, that she'd been invited here for a very specific purpose.

She could hear the door lock, but, after the sound of the Nanny's footsteps retreated down the hall, she scurried over to it anyway. She hadn't wanted to keep track of a purse big enough to hold her wand all night, but she had been working on more magic she could do without it, and the fine inner workings of the lock were perfect for that. Everything was very small, and, as long as she concentrated, she should be able to move them around without too much trouble.

She closed her eyes, thinking hard, reaching out with her magic, pushing away the throbbing of her bottom, and the anxiety of the Nanny returning and finding her out of the corner. After a long moment, she heard a click, and the doorknob turned.

Smiling, she slipped out, and back down the hallway, closing the door behind her, and even managing to lock it again, to delay the discovery of her absence an extra moment or two. She winced as she hurried along, rubbing her backside, then blushed as she felt skin, realizing she'd forgotten to pull her dress back down. Good thing she'd realized it before she got back out to the party! She probably wouldn't have gotten far if her wet undies and pink bottom were on display!

She skirted her way along the edge of the party, making her way slowly but surely around the room, back to the front door, and out. It might take a few minutes to get a ride there, but she knew she'd feel better outside, where it would be easier to get away if the Nanny came after her.

She really thought she'd made it, too, as she walked down the driveway, disappointed that this was the way her New Year's Eve was ending, though happy it hadn't been in a diaper. And then she heard a sound behind her. She froze for a moment, thinking it must be the Nanny, but that wasn't what it sounded like at all. No, it was more like the sound of wings. She turned, eyes widening as she saw a huge bird flying towards her, flapping its enormous wings.

Maybe it didn't notice her at all, and was just going to float overhead, but Sierra wasn't about to risk it. She broke into a run, eyes scanning the immaculately trimmed lawn, looking for a tree, or something to hide under, the block the bird from getting to her. She barely made it ten feet before she felt claws closing around her, however, lifting her kicking feet off the ground.

"Let me go!" Sierra squealed, thrashing, trying to break free now, before it got her too high, and the fall from doing so might lead to some serious injuries. She closed her eyes as she felt the claws close tighter around her, wishing she'd gone with the bigger purse after all.

"I don't think so, young lady!" Sierra opened her eyes, finding the Nanny standing over her, glaring down. "You could've seriously gotten hurt, running around out here in the middle of the night! Not to mention, I specifically told you to stay put!"

The second spanking, out on the lawn, was even worse than the first, and her bottom was bright red as she was marched through the party, dress up in the back and panties around her ankles, giving everyone a perfect view as she was taken back to the guest room and taped into a thick, poofy diaper.

Her fancy dress was taken away, replaced with only a baby blue shirt, lined with white lace, that stopped well above the waistband of the diaper, a pair of baby blue padded mittens and booties, and a pacifier. She was led out of the room, diaper crinkling away as she waddled at the Nanny's side, up to an oversized child's bedroom, where another girl, around Sierra's age, was waiting, in a frilly nightgown.

"She's so cute!" Bethany grinned, hurrying over, scooping Sierra up in a hug. Sierra didn't see the bulge of a diaper under her nightgown, but she was sure there was a slight rustle, perhaps that of a pair of training panties instead. "She's perfect, Nanny!"

"I knew you'd like her," the Nanny smiled. "And she's going to do everything you tell her, aren't you?"

Sierra swallowed, staring up at the woman, rubbing her throbbing bottom.

"The one you got me for Christmas didn't," Bethany sulked. "Is this one really going to be better?"

"Why don't you see?" the Nanny suggested.

Bethany eyed Sierra hungrily. "Okay, dolly," she said finally. "Mess your diaper."

"Wh-What?!" Sierra gasped.

The Nanny cleared her throat, giving Sierra a meaningful look. Sierra squirmed, looking around the room, hoping for some inspiration, some way to get herself out of this, before realizing that, at least at the moment, there was none.

Off in the distance, she could hear a chant starting up, a joyous, "Ten! Nine!"

She was supposed to be down there! She was supposed to be getting ready to drink her first glass of champagne, like the grown-up she was! Instead, she was blushing bright red, crouching down, feeling Bethany and the Nanny's eyes on her as she started to push obediently, eyes shutting for some privacy.

When she opened them, everything was different. She blinked, confused to find herself no longer in Bethany's bedroom, but a large, white space, along with one other person. Unfortunately, her clothes had not changed, and, with the position she was in, they felt more babyish than ever, even as she stopped pushing, clumsily scrambling to stand up straight, feeling a sticky streak in the seat of her pants, but not much more than that, luckily.

That was far better than what she saw the one other person there was dealing with. The other girl was a blonde, too, though her hair was quite a bit longer than Sierra's. She looked a good bit, taller, too, and, while she didn't have mittens or booties, she was in a pink bonnet that kept her looking quite babyish, and the matching pink shirt was far smaller, leaving her cleavage on display, trying to burst free, reminding Sierra of how little of that she had herself, even if the neckline of her shirt hadn't been cut so much more modestly.

The main thing Sierra noticed was also bigger, but she wasn't jealous of it at all. The girl was diapered, too, but her diaper was almost comically huge, and stained, very obviously used. Sierra blushed, unable to keep from staring, nose wrinkled, feeling bad for her. She was so distracted, it took her a few seconds to see the sash, looped over one of the girl's arm, declaring, 'Happy New Year 2020.'

"Oh, no!" the girl exclaimed, Sierra feeling bad at first, even if she hadn't chosen this, thinking the girl was upset that Sierra was seeing her this way. "The stork got you?"

"The stork?" Sierra frowned. That could have been the bird she'd seen, she mused.

"Yeah," the girl nodded. "The stork. It goes out every New Year's Eve, searching all the different dimensions, looking for Baby New Year. It got me last year, and..." She gestured down at herself, the implication clear.

Sierra whimpered, looking at the girl, and then herself. Was that really going to happen to her?! "I-I don't wanna be Baby New Year! Why me?!" Sierra pouted, poking at the diaper again, though she doubted she'd have been able to get the tapes off, even without the mittens. This was clearly some deep, ancient magic, and she was going to be no match for it, especially without her wand.

"I know you don't," the girl told her gently. "Listen, my name is Yang."

"S-Sierra," the witch introduced herself, sniffling.

"Sierra," Yang nodded. "Listen, this is a very crucial moment. You're here because the stork claimed you, and then you started to fill your diaper at midnight. That's what it takes. But I think I've found a loophole, but you have to trust me, okay? You only get one shot at this!"

"O-Okay," Sierra nodded, wiping her eyes, listening intently. "What do I have to do?"

"You're not going to like it," Yang warned. "But we have to work fast. In order to be Baby New Year, you have to be in that diaper at midnight. Unfortunately, you can't take that diaper off, and neither can I."

"Well, what can we do, then?" Sierra asked.

"Time works differently here. It isn't exactly midnight, but I imagine it's close, right?" Sierra remembered the countdown she'd heard, and nodded. "We have a little more time here, but not much. You were starting to mess yourself, weren't you?"

Sierra blushed, not wanting to admit to it, even in someone in a far dirtier diaper than she'd ever seen, much less been in herself. If she was telling the truth, though, this wasn't the time to worry about protecting her dignity. "Y-Yeah," she admitted. "I-I think I can hold it, though."

"No!" Yang shook her head. "That's the mistake I made, and the person who was here before me! The stork put its mark on us, and then we wound up in diapers, and about to fill them at midnight, but we thought if we stopped it before then, it would stop the magic."

"I-It didn't?" Sierra sucked nervously on her pacifier.

"Of course not!" Yang gestured to her enormous diaper again. "But I think I know the secret! Changes only happen at midnight, but me and the last person made sure we didn't need one then, and screwed everything up for ourselves. We started to mess ourselves, but hadn't gone enough to deserve a change, and got stuck here. I think the thing to do is to just let go, and earn yourself a change, and then you'll get this over with, and we'll both get a change and get out of here."

"B-But..." Sierra pouted, not wanting to mess herself if she didn't have to, knowing that, even if she got out of here, she was going to end up back with Bethany and the Nanny. Seeing the alternative, however, and without time to debate it, or try to come up with another solution, she gave a resigned nod, and squatted down again, face turning red as she started to push once more.

She wrinkled her nose, feeling the diaper swelling up around her, ballooning outwards as it began to fill in earnest. She felt the mush spreading through her padding, wriggling in place, certain that had to be enough to get her a change, but unable to make it stop now, feeling a little panicked as it kept going, her diaper growing more and more as she continued to mess it helplessly.

"Much better," Yang grinned, Sierra glancing up at her to see her standing in front of her, looking the way Sierra wished she could have at the party. The dress Yang was in was far skimpier than any Sierra would have chosen for herself, or could have hoped to pull off, showing off the girl's long legs and ample cleavage, neither of which Sierra had to be able to flaunt in the first place. She was definitely not in her diaper anymore, that was certain. Confetti rained down around her, and, when Sierra looked at herself, she saw a sash on her now, saying, 'Happy New Year 2021.'

"Oh, Sierra," Yang shook her head, taking a sip from her glass of champagne. "Since you messed your diaper at exactly midnight, you just became Baby New Year!"

"B-But you said..." Sierra grunted, sniffling.

"I should warn you," Yang continued, "that the state of your diaper right now depends on how bad the previous year was... And I think you know how that went. It was pretty rough, throughout all the dimensions, so you're starting off in pretty bad shape." She bent down, giving Sierra's diaper a pat. "Sadly, you won't be getting a change until next year. Enjoy!"

"N-No!" Sierra shook her head angrily. "Y-You told me I'd get a change at midnight!"

"Sure," Yang shrugged. "Midnight, next New Year's Eve, as long as the stork finds someone else, and they do their part. It looked like you might have been able to stop it, so I had to give you a little push to keep you from doing that, that's all. I wasn't about to let myself be Baby New Year two years in a row."

"That's not fair!" Sierra tried to stand up, to face Yang, but her diaper was already so full, it was a struggle to even do that much. And the year had barely even started! That was quite the testament to how bad the previous year had been, though that wasn't much of a comfort in the moment.

"Don't worry," Yang took another sip of her champagne, patting Sierra on the head. "You'll be taken care of here. Someone will be by to feed you your breakfast in the morning. I hope you like oatmeal and prunes!" She chuckled, walking off, vanishing into the void, back to her own dimension, leaving Sierra all alone as a crib rose out of the floor beneath her, indicating that it was time for her to go to sleep, so that she could wake up to face the first of what was bound to be a very long 365 days.