Author's Note
Yes I know this has been done to death already but I decided to give my own take. Do enjoy. 
Prologue
Many years ago the magical land of Equestria was just ending its golden age. Two Princesses ruled the land. Their names were Princess Celestia and Princess Luna. Celestia’s job was to raise and lower the sun while Luna raised and lowered the moon. The two sisters kept peace harmoniously but then everything went wrong...while the civilians of Equestria played and loved the sunlight they slept and shunned the moon. Luna became jealous of her sister and one day wouldn’t lower the moon. Not only was this bad for the citizens of Equestria but bad for the people in other parts of the world because the sun wouldn’t go down. There was serious risk of drought and famine in all the lands. Celestia desperately pleaded with her sister to lower the moon but Luna refused. Luna then went through a horrible transformation. She was no longer Luna but the being known as Nightmare Moon. The two sisters fought hard and Celestia reluctantly called upon the ancient artifacts the Elements of Harmony and banished her sister to the moon. Celestia then took the..
“job of raising and lowering both the sun and the moon.”
The young lavender mare said finishing the story. Twilight Sparkle a young mare of 17 and Princess Celestia’s personal student. Being Celestia’s student her popularity in Canterlot is very high and she got the honor at the young age of 7. She was a prodigy in Magic one of the best. Many girls wanted to be her friend, only one small problem. She doesn’t have time for friends. Always has her nose buried in a book and always having to keep things well and organized. Which is especially hard on her assistant/“brother” Spike who is Celestia’s adopted son, and who Twilight personally had to outwit to get Celestia’s attention. Spike is Twilights only real friend and their bond is very strong.
“Hmm Elements of Harmony. I know I heard those before..but where?” Twilight thought. Twilight then decided to dash back to her home. She packed up her book and began the run back. Along she way she bumped into three ponies; Minuette,Lemon Hearts and Twinkleshine.
“Hey Twilight Moon Dancer is having a small get together in the west courtyard wanna come?” Lemon Hearts asked.
“Sorry girls I got a lot of studying to do.” Twilight said trying hard to look innocent before dashing off again.
“Does that girl do anything other then studying? I think she’s more interested in books than friends.” Lemon Hearts exclaimed.
Twilight reached her home and bust open the door.
“SPIKE!” Twilight called before seeing him on the ground for he was standing in front of the door when Twilight bust it open.
"Ow.." Spike groaned out.
Spike was the same age as Twilight except Twilight was a few weeks older, he was well built for a dragon, he had purple and green scales and a pair of wings to top it off which came in handy when heavy loads needed to be transported quickly.
Twilight dashed upstairs to the library.
"Quick find me the book about predictions and prophecy's." Twilight demanded before noticing a small ruined box on Spike's tail.
"What's that?" Twilight asked.
"Well it was a gift for Moondancer but.." Spike began before the destroyed teddy bear fell out. Twilight then started rifling through books.
"Oh Spike you know we don't have time for that shit." Twilight scoffed.
"But Twilight we're on break." Spike explained.
Twilight levitated some books down looking at the covers of each.
"No. No. No no no. Ugh SPIKE!" Twilight shouted. Spike was a bookshelf away holding a book.
"Over here." Spike shouted tossing the book at Twilight who caught it with her magic causing the other books to drop. Twilight walked over to her desk leaving the books in a mess. Spike sighed before beginning to pick them up. Twilight flipped through the pages.
"Elements Elements..AHA Elements of Harmony! See Mare in the Moon?" Twilight asked herself.
"Mare in the Moon? Come on that's just an Old Pony's Tale." Spike said.
"Mare Mare..AHA Mare in the Moon! A myth from old times. A powerful pony hellbent on ruling Equestria,defeated by the Elements of Harmony and imprisoned in the moon in the moon. Legend has it on the longest day of the 1000th year the stars will aid in her escape and she will bring about Eternal Night! Oh my god..LUNA!" Twilight gasped.
"Spike do you know what this means?"
"Uh no." Spike answered. Twilight handed him a scroll and quill.
"Take a note to Celestia." She said.
"Ok." Spike replied writing down everything Twilight said.
"My dearest teacher, my continuing studies of pony magic have led me to discover that we on the brink of disaster. For you see the mythical Mare in the Moon is infact Nightmare Moon,your sister! And she is about to return to Equestria! And bring about eternal night! Something must be done to make sure this terrible prophecy does not come true! I await your quick response. Your Faithful Student Twilight Sparkle. Now send it."
"Now?" Spike asked.
"Yes now." She replied.
"But Twilight she's a little busy getting ready for the Summer Sun Celebration. It's The Day After Tomorrow!" Spike pointed out.
"That's just it. The Day After Tomorrow is the 1000th year of the Summer Sun Celebration. It's imperative the Princess is told right away!" Twilight explained.
"Alright but don't say I didn't warn you." Spike said before breathing his dragon fire on the note sending it to Celestia.
"Oh I'm not worried Spike. Your mother trusts me completely. In all years she's been my mentor she's never doubted me." Spike then burped out Celestia's reply. He opened up and began to read.
"My dearest most faithful student Twilight. You know that a value your diligence and that I trust you with my life." Spike began. Twilight looked out the window with a bit of a smug look on her face.
"But you simply must stop reading those dusty old books!" Twilight gasped in shock.
"I do have a task for you however. There's more to a young ponies life then just studying so I'm sending you to oversee the preparations of the Summer Sun Celebration in this years location..Ponyville. In this note you will find a full checklist of tasks that need to be done. I also have another task for you to complete. Make some friends! I have arranged for you to stay in the library." Spike said finishing the note. Twilight sighed in defeat. Spike smirked a bit.
"I warned you. You may be Celestia's student 10 years running but I'm her son. I know her better then anyone. But hey look on the bright side the princess arranged for you to stay in a library. Doesn't that make you happy?" Spike asked.
"Yeah I guess." Twilight sighed.
"Well there's no fighting it I might as well prepare a carriage." Twilight walked off to the carriage room.
"I need a ride to Ponyville." Twilight requested.
"Yes ma'am." One of the drivers said before him and his co driver got themselves ready. The carriage took off with Spike in tow west towards Ponyville. Both Spike and Twilight were blissfully unaware at just how much everything will change..
"Twilight you've been really rude to everyone," Spike said in a rather disappointing tone.
"Sorry Spike but I have to convince the Princess Nightmare Moon is coming and we're running out of time! I need to be alone so I can study without some psychotic people trying to make friends all the time. Now, where's the light?" Twilight asked looking around the library only for the light to be clicked right on revealing a large gathering of people in the library.
"SURPRISE!" Ballons and decorations were all over the library and all sorts of food and beverage you could imagine.
"Celestia damn it." Twilight groaned.
Suddenly Pinkie Pie popped up.
"SURPRISE! My name is Pinkie Pie and I threw this party just for you! Were you surprised? WERE YOU WERE YOU?" Pinkie asked jumping all over the place as if she snorted a large amount of cocaine before showing up.
"Oh yes very surprised!" Twilight answered.
"But libraries are supposed to be QUIET!"
"Oh, that's silly! What kind of welcoming party should be quiet? I mean duh LAAAAAME!" Pinkie said. Twilight tried walking away but Pinkie followed talking nonstop. Twilight walked up to the table and started pouring what she thought was whiskey while Pinkie was still talking. She starting taking a sip.
"AND NOW YOU HAVE LOTS AND LOTS OF FRIENDS!" Pinkie said excitedly as the folks Twilight talked to earlier popped up behind her. Twilight's mouth then started to burn.
"Are you alright sugar cube?" Applejack asked. Twilight then jumped up tears coming out of her eyes and ran off for water.
"Aww she's so happy she's crying!" Pinkie said.
Spike then picked up the bottle and looked at it.
"Hot Sauce." Spike said. Pinkie then poured a bunch of it on a cupcake and ate it much to the shock of the other girls.
"What? It's good!" Pinkie said. Spike then got an idea.
"Pinkie you like Hot Sauce right?" Spike asked smirking.
"Why?" Pinkie asked.
"How about me and you have a little drinking contest whoever drinks the most Hot Sauce wins." Spike suggested. Pinkie smirked at the idea.
"Oh IT.IS.ON!" Pinkie said before grabbing a table, two chairs and a bunch of hot sauce.
"DRINKING CONTEST!" Rainbow shouted as ponies gathered.
"Alright, buddy what does the winner get?" Pinkie asked.
"200 bits." Spike said placing his bits on the table. Pinkie then followed suit.
"You first." Pinkie said smirking. Spike then drank his hot sauce not even blinking.
"Tasty. Your turn." Spike said to Pinkie who then drank not even phased. The contest went on and on and on for what felt like hours until only two bottles remained. One for each.
"Together.." Spike said.
"Agreed...one...two...three." Pinkie counted before both she and Spike drank the last bottles. Both of them were panting hard however neither felt like passing out.
"There's no more hot sauce?" Pinkie asked.
"None." Someone said.
"Alright...guess we'll call it a draw." Spike said.
"Agreed but this isn't over." Pinkie said with a bit of an evil look in her eye.
"Agreed." Spike replied as music began to sound off. On a makeshift stage was Blood Armor, Big Mac, and a couple other ponies and they were singing a song.
"Girl, you really got me goin'. You got me so I don't know what I'm doin' now. Yeah, you really got me now. You got me so I can't sleep at night. Yeah, you really got me now. You got me so I don't know what I'm doin' now. Oh yeah, you really got me now. You got me so I can't sleep at night. YOU REALLY GOT ME! YOU REALLY GOT ME! YOU REALLY GOT ME!" Big Mac was singing with the others backing him up. The party lasted nearly all through the night much to the dismay of Twilight who was upstairs trying to sleep.
Spike then barged in.
"Twilight! Pinkie's starting pin the tail on the pony! Wanna play?" Spike asked.
"NO! Do you have any idea what time it is? These people are crazy!" Twilight shouted.
"Twilight it's the eve of the Summer Sun Celebration. You have to stay up you'll miss the Princess raising the sun. You really need to lighten up Twi." Spike pointed out before leaving.
Twilight rolled over and began thinking to herself.
"Celestia here I thought I'd spend more time studying the Elements but NOPE! They just had to throw a damn party!" Twilight then turned over and looked at the moon thinking back to the legend.
Spike then burst back into the room.
"TWILIGHT COME ON IT'S TIME TO WATCH THE SUNRISE!"
The ponies gathered in the town hall waiting. The girls were huddled together.
"ISN'T THIS EXCITING? ARE YOU EXCITED BECAUSE I'M EXCITED! I'VE NEVER BEEN SO EXCITED! Well except for the time I first saw you and I went HUUUUUUUU but really who can top that?" Pinkie said quickly. Fluttershy then started directing the birds as the light shined on the Mayor of Ponyville; Mayor Mare.
"Ladies and Gentlemen as Mayor of Ponyville it is my great pleasure to announce the beginning of the Summer Sun Celebration!" Mayor Mare said. The crowd cheered.
"In just a few minutes her royal highness Princess Celestia will appear and we will witness the magic of the sunrise and celebrate the longest day of the year!" Twilight looked at the moon and to her horror, the shadow that was usually on the moon was gone!
"Now it is my great pleasure to announce the one that gives us the sun each and every day, the good, the wise, the bringer of all harmony in Equestria...PRINCESS CELESTIA!" Mayor Mare shouted jovially. Rarity pulled the curtain and the birds began to sing...only to find the Princess was gone!
"Oh no. This can't be good." Twilight said fearfully as whispers rose up.
"Remain calm everyone there must be a reasonable explaination!" Mayor Mare said trying to restore order but it was clear she too was confused. Rartiy came back from behind the curtain.
"SHES GONE!" Rarity shouted. Gasps and whispers sprang right up. Suddenly a black mist appeared at Rarity's feet. She jumped from the balcony right into Spike's arms.
"You okay?" Spike asked. Rarity blushed.
"Yeah, I'm fine." Rarity answered as Spike put her down.
'Oh no..." Twilight whispered. The black mist parted and standing there on the balcony was Nightmare Moon...
"Nightmare Moon!"
"Oh, my beloved subjects..." Nightmare Moon began.
"It's been so long since I've seen your precious little sunlight faces."
"WHAT DID YOU DO WITH OUR PRINCESS?!" Rainbow shouted as both she and Blood swooped in for an attack. Nightmare Moon easily blew them back up against the wall and chuckled.
"Am I not royal enough for you?" Nightmare Moon asked.
"Don't you know who I am? Does my crown no longer count now that I have been imprisoned for 1000 years? Did you not recall the legends? Did you not see the signs?" Nightmare Moon asked.
"I did! And I know who you are! You're the Mare in the Moon! Nightmare Moon!" Twilight shouted. Gasps filled the room.
"Well well well someone who remembers me. And you also know why I am here?" Nightmare Moon asked. Twilight was silent as she lost her courage. Luna chuckled more.
"Remember this day fools. For it was your last. From hence on THE NIGHT WILL LAST FOREVER!" Nightmare Moon shouted laughing like a maniac as mist surrounded her and lighting and thunder filled the room with sound and light. Twilight looked on in fear...