It has been a while since Celestia has asked Luna to wake up earlier than normally. Since she was cured from her dark side, it occured only when there was an emergency, or a great celebration. But this night was calm, and she couldn't possibly imagine what could be this important.
She was well aware that it was her birthday, but she remebered her birthdays being a nice calm dinner between her, Celestia and the few friends she had at this time, which were all dead by now, and the only new, real friends she had made were her saviours, the five ponies from ponyville and Celestias student and new princess, Twilight Sparkle.
As she walked through the halls of the castle, she thought about what could possibly have happened. It was most likely an unpredicted emergency. Her sister was always well informed and highly intelligent, which let her predict future events with a frightening precision, but she wasn't always right, and in some cases even she was surprised.
Well, it wasn't the griphons, that was clear. Celestia was always right about the cases which involved griphons, and she predicted that they would attack again, but there were still centuries ahead, at least as long as there is no outside force taking action. She was more worried about the changelings, which were still present in Equestria, even if they are passiv at the moment.
Luna didn't immediately realise that she had gone past the door to the throne room, until she had reached a wall before her she didn't expect. She returned, looking around if anyone has seen her, but except for the guards, none were there, and the guards never spoke to anyone about the things happening inside the castle, expect to Celestia or Luna herself.
As the door opened, she noticed that not only Celestia, but also Twilight Sparkle and Cadance were sitting there. She would have been worried, if not for the smiles on all three on their faces. She walked in, calmly, but nonetheless curious what could possibly be the case of this meeting.
"Happy Birthday", the three said together, and Luna couldn't prevent herself from blushing and grinnig. It has been such a long time since she had heared this words, and it made her happier than she had thought for herself.
"Thanks, but what is the occasion of this all? I don't think you called me here just to gratulate me for my birthday. There has been some reason, isn't there?" She regretted to ask her this question the moment she saw the look on Celestias face. The grin was gone, and a worried look has taken over.
"You are right, there is a urgent thing we have to discuss. It is about an old enemy we have to talk: Nightmare Moon. I know you might think that she is gone for good, but the evil inside a pony never entirely vanishes, not within you" she sighed "and not within me. There is also a dark side within me, and I am afraid it might break out, freed from my guilt of banishing you. I need your advice, dear sister. You are the only one with experience in such things."
Luna was startled. Celestia needs her help with something even she had to succumb? And not only that, something was off, but she was to deep in her thoughts to notice what it was. There was only one thing she knew to do in this situation: "Tia, don't feel any guilt banishing me. You had to do it, or else I would have destroyed not only Equestria, but the whole world. I didn't only forgive you, I feel glad that you banished me, because it gave you all a chance to really safe me."
The slight smile on Celestias face calmed Luna for a bit, but not enough to feel safe right now. She was afraid to be to weak to safe Equestria from her sister if she ever turned evil, because she thought she was weaker than Celestia. What she didn't realise was that they are equal in power, Luna was only afraid to use her full power after what she did.
"Luna, I know that you feel no anger towards me anymore, but it isn't as easy as that. Please follow me, I need to show you something." With these words, she turned her flank towards Luna and walked on the balcony. Luna followed her, not knowing what would happen next. Twilight and Cadance walked besides Celestia. As Luna reached the balcony doors, she noticed that all three of them looked first towards the rised moon, and then in the castle gardens.
Luna walked forward, and as she reached the edge of the balcony, a loud "Happy Birthday" reached her, said by all of Canterlot and even more ponies. She looked towards Celestia, which was smiling again.
"Sister, your evil side awoke after you realised that no pony was awake during your beautiful nights, which you cared for. Therefore I made an arrangement with the people of Equestria. Each month, there should be one night in which they were awake and celebrating your return, and each year, on your birthday, a night long party should participate. What do you think, do you like it?"
Celestias look showed real worry, because even she couldn't predict the actions of a fellow alicorn. And Luna, whose eyes were wet, finally realised what was off before: Twilight and Cadance both were still smiling, when Celestia talked about her dark side. Luna knew that Celestia told the truth, she could tell when her sister tries to lie, therefore it was difficult to notice it was a trick.
"Tia, I, I, I love it" Luna said, in low voice. She started to cry, and Celestia put a wing around her sister, comforting not only her sister, but also herself. The ponies below were silent, awaiting a response from above. Luna noticed the silence, and from under her sisters wings, with the royal canterlot voice, she started the night: "FELLOW PONIES FROM EQUESTRIA, MAY THIS NIGHT AND ONE NIGHT EACH MONTH BE A NIGHT OF GAME AND FUN, A NIGHT WHERE THE STARS AND THE MOONS ARE CELEBRATED. MAY THE PARTY BEGIN."
The ponies couldn't hold it back anymore: screams of joy were echoing through Canterlot, and the whole night was one party. Lunas Saviour entered the throne room, they were waiting for exactly this moment. A huge banquet was hold in the castle gardens, while the princesses and heroes of Ponyville were eating on the balcony. It wasn't a simple night, for Luna it was a present, one worth far more than anything worldly she could have got by her sister.
The other present she became were important to her nonetheless. The cakes, the decorations, the pictures, everything she got this night was put in a room near the throne room. This room should later be known as the "Room of the night", and it was Lunas most precious room from this night on, on par with the observatory.
In this night, not only Luna got a present, but Nightmare Moon too. As she was part of Luna, she was affected by what happened to her, to a certain degree. And that the ponies were willing to spend a night each month awake, celebrating the night, let even her smiling, and hoping that one day, the ponies will stay awake in the night and sleep during the day. With this thought, Nightmare Moon was put into a slumber she would never awake again,.