So Rick Riordan (author of Percy Jackson, obviously) tweeted that we will discover Annabeth's birthday in the House of Hades. My friend and I were talking about it and we starting spitting out headcanons and stuff. We came up with this idea and I just happened to write it down. I don't know Annabeth's actual birthday or if it will come up in the House of Hades like Jason's did in Mark of Athena. I also don't know if it will really be too important to the plotline. However, this is just a little oneshot my friend and I came up with. Enjoy and review!

The Most Important Moments

They sat on the edge of a rock, huddled close together, listening to nothing but their breathing. Days like these seemed to go by slowly. They were constantly being pursued by the worst monsters of mythology, narrowly escaping the clutches of baddies like Medusa and Arachne on several occasions. At the end of the day, they were lucky to still be alive. Sometimes, after a long day of battling monsters and traveling the depths of Tartarus, Percy and Annabeth would have little to say. They liked to be close to each other and relaxed as they silently listened to whatever surrounded them. Hearing each other's breathing, heartbeat, and occasional shifting of positions was enough to satisfy them with the thoughts of being alive.

Percy's arms were wrapped around Annabeth as they shared the rock, their backs resting against the wall of Tartarus. It was cool against their backs, being made out of solid celestial bronze. Percy was lost in his own thoughts, wondering how close they were to the Doors of Death. How many more hours would have to spend fighting monsters that would just simply return back to Tartarus once he killed them? He slowly began to drift off with these questions lingering in the back of his mind. Just as his head rested against the wall, something caught his eye.

"Hey!" Percy exclaimed, sitting up abruptly. Annabeth twisted around in his lap so she could face him.

"What's wrong?" she asked, her forehead creasing in worry. Percy ignored her question and grabbed her arm. He pulled it up to his face so he could examine the metallic watch wrapped around her wrist.

"It's midnight," he stated.

Annabeth glanced at the watch. Leo had made it for her a couple months back as a thank you gift for helping him with the mechanics of the Argo II. The gift came to her as a shock—Annabeth thought she should be thanking him. Either way, Leo insisted on giving her the watch. It was a cool device, definitely a one-of-a-kind: made out of pure celestial bronze, it was always cold against her skin. Besides being able to tell the time, it had a GPS tracking system built within it, so Annabeth would be able to know where she was at all times. Annabeth often checked it, but the watch probably wasn't built for the depths of Tartarus. Right now, it didn't know where she was in the world.

The watch also came with a built-in flashlight, alarm clock, and laser pointer, though she didn't know what she would need that for. She wished Leo could have added an expandable shield to it like Percy's old watch, but it seemed like he would need Tyson for that job.

She looked at Percy, who was gazing at her, waiting for her to catch on to something. Pure excitement was written all over those sea-green eyes. He had one of his crooked smiles plastered to his face, something that always made butterflies flutter in Annabeth's stomach. When it was clear Annabeth did not know what her boyfriend was up to, Percy sighed.

"It's a whole new day," he said carefully. He was nudging her toward something important. But what could it be?

"Yeah," muttered Annabeth. "We're lucky to have made it another day."

"Well," said Percy matter-of-factly, "I think today will be more important than the others."

Annabeth raised an eyebrow. "What makes you say that? Are we closer to the Doors?"

Percy's smile didn't even waver. He adjusted his position so he could see her whole face.

"Annabeth, how long have we been down here?"

The daughter of Athena looked back at her watch and did some quick mental math.

"Almost five days."

"And we fell in on what day?"

Annabeth thought for a moment. "July 1st."

Percy's smile grew. He couldn't keep the excitement from his voice. "And that would make today…"

Suddenly, Annabeth's eyes widened in realization. She let out a little "Oh…" before turning her back on her boyfriend, biting her lip anxiously.

Though she couldn't see Percy, she knew he was frowning. Annabeth cursed herself. She hated it when Percy was upset, let alone it being about her.

"What's wrong?" said Percy worriedly. "Why aren't you excited?"

"I—I don't know," she admitted. "I hadn't realized the date. I actually forgot it was even coming up."

Percy forced Annabeth to face him. He could see the sadness in her eyes. Of course she hated being down here, especially on a day like this. She should be back at camp, celebrating with her friends and siblings from the Athena cabin. Percy wished with every fiber of his being that she could be anywhere other than here. Even celebrating with a few select demigods on the Argo II would be better than being alone in Tartarus with a boyfriend who couldn't even give her a birthday present.

"You didn't realize your birthday was coming up?" Percy asked in disbelief. "I mean, I know we're older now, but even I still get excited for my birthday."

"You didn't seem too excited last year," Annabeth pointed out. Percy shrugged.

"I had a prophecy to worry about. Besides, I didn't think I would live long enough past that date."

"Okay," Annabeth said, sounding like she was about to make an important point. "You worried about a prophecy; I was worrying about my quest. Those are things that can keep us from remembering something as silly as a birthday."

"Whoa," Percy said, unwrapping his arms from his girlfriend. He did the time-out signal with his hands. "Hold up. Birthdays are not silly."

"When it comes in the middle of a war, I think it is."

Percy's eyebrows scrunched together, another thing Annabeth found adorable. She tried to keep a straight face. She was not losing this argument.

"You don't really think that, do you?" Percy sounded hurt.

Annabeth pinched the bridge of her nose. A migraine was coming on, something she frequently got lately. All the stress about her solo quest, the Doors of Death, the Greek and Roman battle, the Giant War, and Gaea rising was really getting to her. The last thing she needed was to worry about a stupid birthday—especially hers.

Annabeth's expression was enough of an answer for Percy. He took her hand and they sat in silence for a few moments. Then, to both of their surprise, Percy started singing. He didn't know what overcame him, but he was determined to celebrate Annabeth's birthday, even if she didn't want to herself.

"Happy birthday to you!"

Annabeth stared at him incredulously. "What?"

"Happy birthday to you!"

"Are you singing?"

"Happy birthday, dear Annabeth!"

"In Tartarus?"

"Happy birthday to you!"

Percy finished and gave her the biggest smile ever. At first she just stared at him, thinking maybe Tartarus caused him to lose a bit of his sanity. And then she started laughing.

Percy frowned. "Oh no, you're laughing at me."

Annabeth continued to laugh, to Percy's dismay. He groaned and put his head in his hands.

"I know it was a little off key," he whined, "but I didn't think it was that bad!"

Her laughing was reduced to giggles. Percy's face was now beet red. She quickly suppressed the rest of her laughter and was able to calm down.

"Percy—"

"I know, I know," he said sadly. "I'm a crappy singer."

"No, Percy—"

"Gods, Annabeth, I'm really sorry."

"Percy!" His head snapped up at her voice. They made eye contact and he saw joy and happiness in her eyes, something he hadn't seen in a while.

"It was beautiful, Percy," she continued, a smile played out in her lips. "Worthy of the Apollo cabin."

Percy grinned widely. "You think so?"

Annabeth leaned against him, allowing him to wrap his arms around her again. They rested against the celestial bronze wall. "I know so."

Silence washed over them. Soon, Percy could hear Annabeth's breathing slow, signaling that she was asleep. He felt like he could take a twenty hour nap himself. He kissed the top of her head and closed his eyes.

"Happy birthday, Annabeth," he whispered.

Annabeth woke up in the comfort of her own bed. The feeling of waking up to actual light, the warm sheets around her, and being in clean clothes sent a buzzing feeling throughout her. Just yesterday, by some chance of a miracle, she and Percy found the Doors of Death. With the help of her friends, they were able to close the Doors and fend off the monsters of Gaea's army that were guarding them. They suffered no casualties, only a few injuries—none major—and everyone was able to hobble back to the Argo II in one piece. Percy and Annabeth were finally able to leave Tartarus behind them.

Annabeth got out of bed, feeling tired but rested. She pulled her hair back in a messy pony tail and glanced down at her clothes. She was wearing pajama shorts and an oversized purple Camp Jupiter shirt. Everyone had under-packed for the quest, and Annabeth was the first person to actually run out of shirts. Jason was the only person with a leftover t-shirt and thankfully gave it to her to wear. At first, it felt weird to wear a camp shirt that wasn't orange or part of Camp Half-Blood; she soon got over it and now hardly minded.

Still too tired to do much of anything, Annabeth stumbled out of her room on the Argo II, not bothering to change into jeans or put on shoes. Her ankle was healing slowly but surely (with the help of lovely demigod healing food), and she was now able to limp on it without much support from anyone. Her stomach grumbled in hunger. When was the last time she had an actual meal? She checked the watch still attached to her wrist. She had overslept—it was nearly two o'clock in the afternoon.

I guess I missed breakfast, she thought.

Something crinkled underneath Annabeth's foot as she stepped into the hallway. She looked down and found that she had stepped on a piece of paper. She removed her foot and saw a large black arrow printed on the paper. Her eyebrows creased as she looked ahead to see several identical papers placed one after another, disappearing down the hallway. It was a path.

Annabeth followed the path of arrows. They led her throughout the ship, down different hallways and taking several unnecessary turns. Whoever set up this path wanted to throw her off as to where it would be taking her. She wondered what was going on.

The arrows suddenly stopped. This part of the ship was dark, but she knew exactly where she was, which was ironic, because she was going to head here anyway. She walked into the mess hall and felt around for the light. She flipped it on and nearly had a heart attack.

"SURPRISE!" eight distinct voices rang out. Annabeth jumped back and had to use the wall for support so she wouldn't fall over. The mess hall was decorated for a party: balloons, confetti, and streamers were everywhere. Her friends had popped out of their hiding spots and all had big grins on their faces. It took a moment for Annabeth to regain her senses.

"What—?"

"Come on, Annabeth," Leo said playfully. He wrapped his arm around her shoulders—something she would not allow him to do under normal circumstances—and led her to the center of the mess hall. "Don't you know a surprise party when you see it?"

"But—"

"It's your birthday," Piper said, raising her eyebrow. "Isn't it?"

"Well, yesterday, but—"

Percy came over to her with a birthday hat and placed it on her head. Looking around, Annabeth noticed that everyone had one on, including Coach Hedge, who didn't look too pleased with it. At times she would feel ridiculous wearing one, but at the moment she was too flustered to feel much of anything other than shock. Annabeth usually was not one to be caught off guard. Today was obviously an exception.

"I told them," Percy said sheepishly, answering Annabeth's unasked question. He gave her a small smile and playfully shoved Leo off her, taking his place in wrapping his arm around her. "I know you're not one for big parties, but I felt like Tartarus wasn't an ideal place to spend your birthday."

"I heard they don't even have cake down there," Leo said, flashing them a crooked grin. Piper punched his arm in annoyance.

"How did you guys manage to set this all up?" Annabeth asked in awe.

"Leo made a quick stop at a party store while you were asleep," said Jason. "From there, it was simple. Frank and Piper blew up the balloons, I put up the streamers, Nico and Leo had a little too much fun throwing confetti everywhere—" the boys gave Annabeth a sheepish grin, even Nico, "—and Percy and Hazel baked a cake."

"I made the path of arrows from your room to the mess hall," Coach Hedge butted in.

"Yes," Annabeth said dryly, "thank you for unnecessarily leading me all over the ship."

"You're welcome, cupcake."

"Speaking of cake," said Percy eagerly, "can we please eat now?"

The eight demigods and satyr sat around the table. A vanilla cake sat in the center, decorated with blue frosting, sprinkles, and candles.

"Did you know your boyfriend can bake?" Frank asked Annabeth as they everyone got settled.

Annabeth laughed. "That is one thing he's actually better at than me."

Jason glanced at the cake. "I didn't actually know our birthdays were so close."

Annabeth raised an eyebrow. "Is your birthday coming up?"

The son of Jupiter's head popped up as if he didn't realize he said anything aloud. He then shyly looked at his friends. "It was the day you and Percy fell. July 1st."

"Why didn't you tell any of us?" Hazel said gently. She knew what it was like to have a lonely birthday.

Jason shrugged. "I didn't think it was important. Piper and I were having a picnic but that got cut short. I mean, we had giants to battle and you to look for." He gestured to Annabeth. "I didn't really want to say anything."

"Next time, say something," said Annabeth. "We can take a few minutes out of the day to celebrate a birthday."

Annabeth looked at Percy and they shared a smile. That was the point Percy was trying to make last night when they were discussing her birthday in Tartarus. Maybe the son of Poseidon was right. Sometimes, even during a quest, the little happy moments like anniversaries and birthdays were the most important out of anything.

Before she could register what she was doing, Annabeth began to rearrange the candles on the cake, half of them on one side and the other half on the other. Then she positioned the cake between her and Jason.

"We'll share it," she said. Jason smiled with gratitude.

"All right!" shouted Leo excitedly. "Annabeth and Jason's seventeenth birthday bash is a-go!"

"Actually, Leo," Jason cut in, "I'm only sixteen."

"Whatever," Leo said dismissively. "Flame on!" A small flame burst onto his hand, the fire licking the tips of his fingers.

"You better not melt that frosting," Percy warned. "While you and Nico were frolicking through confetti, Hazel and I spent hours making sure that cake was perfect."

Leo had a mischievous look in his eye, and Percy groaned, fearing for the life of his cake. The son of Hephaestus expertly lit all the candles with a wave of his hand. Suddenly, the room burst into the singing of Happy Birthday—even Nico was joining in. Annabeth noticed how the kid looked a little better. He was still weak and hardly smiled, but the son of Hades seemed lighter and happier. Maybe the return of Percy and Annabeth and the closing of the Doors of Death helped relieve Nico of some stress.

As her friends sang, Annabeth looked around at them. They all seemed happier. It was like a giant burden was taken off their shoulders. Hazel and Frank were more cuddly; Piper looked as if she was breathing for the first time in days; Jason was finally relaxing and letting himself smile; Coach Hedge stood back and let the demigods do as they pleased, not being too harsh or shouting at them to be on their guard for the enemy; Leo and Nico had apparently grown close. Annabeth never would had expected the loud and obnoxious son of Hephaestus to become best friends with the quiet, introverted son of Hades—either way, everyone aboard the Argo II was simply happy.

Annabeth and Jason blew out their candles. Piper cut the cake, not trusting Leo with a knife, and soon everyone was eating. During the party, stories were exchanged—what happened on the demigods' way to the House of Hades, and the challenges Percy and Annabeth faced in Tartarus. They even began discussing old stories—Percy's prophecy, Annabeth's time as a runaway, Jason's own quests, Leo's foster homes, Frank's mom, Hazel's school, Piper's dad, Nico's sister, and Coach's battle experience. Not all the stories were happy, not all of them sad, but as everyone talked, the inhabitants aboard the warship grew closer and closer.

Hours later, the whole cake gone (thanks to Coach Hedge's never-ending hunger), and everyone now establishing a best friend status with each other, the demigods and satyr began getting ready for bed. The day went by quickly during the party, and although it was only eight, everyone was tired from the battles that went on the day before. They shoved their dishes in the sink, too exhausted to clean them up tonight, and everyone stumbled to their rooms, calling out a dreary "Goodnight" behind them.

Percy and Annabeth were the last ones in the mess hall. Percy grabbed Annabeth's hand and squeezed it, smiling at her.

"Did you like the party?"

"Of course I did," Annabeth said. "You didn't have to do all that for me."

Percy shrugged. "You only get to experience your seventeenth birthday once. I didn't want your memory of it to be about Tartarus."

Annabeth had to admit: Percy had his moments. Sometimes he could be slow and forgetful, and other times he could be a quick-thinker and the most thoughtful guy in the world. Annabeth was lucky to have him.

They walked back to their rooms and stopped outside Annabeth's door. Before she went in, Annabeth stood on her tip-toes and kissed Percy.

"So," Percy said mischievously, "since your birthday was a huge success—all thanks to your amazing boyfriend—I'm guessing this is a good omen for my upcoming birthday?"

Annabeth playfully shoved Percy and they laughed—something they hadn't done in a long time.

"We'll see how nice you are to me for the next month." Annabeth smirked and disappeared into her room.

Percy sighed. It sure was good to be back.