“Eeeeuuuuuuuuuuuuuurrgh.”
Sunset slumped onto the table, cheek pressed against its surface.
Trixie walked up to the booth and cheerily sat down next to Sunset. “Evening! What’s up with her?”
“Greetings, Trixie,” said Luna. The alicorn’s lips betrayed no trace of a smile, but the way her eyes twinkled strongly suggested she was giggling inside. “I believe that Sunset is distressed over her tri-weekly cycle.”
“Really?” Trixie looked down at the mess of red and yellow mane. “Why don’t you just get some medicine from the hospital?”
“Because I’m going back through the mirror tomorrow, and I don’t know if it might mess with my head.” Sunset groaned and sat up slowly. “Gah! Summer heats are the worst.”
“Agreed,” said Luna. “It is so much milder in autumn and winter. Unless, of course, one happens to be amongst those unfortunate enough to suffer an intense estrus regardless of season.”
“I’m one of them. And in summer it's even worse.”
Luna smiled sympathetically. “I returned from exile during the summer solstice. You can imagine how frustrated I was when I attacked Ponyville.”
Sunset smirked. “This gives an entirely new dimension to you noticing that nopony was wearing pants.”
“Excuse me,” said Luna huffily, “I would have you know that Nightmare Moon was a monomaniacal conqueror, not a pervert. I kept my urges firmly in check, thank you very much.”
Trixie tilted her head. “Uh, just a moment. What’s this about a mirror?”
“Oh, right,” said Sunset. “We still haven’t explained it to you. It’s… complicated. Short answer is: I live in another dimension and over there, everyp… everyone, myself included, is a hairless primate thing with a radically different biology.”
“Waaaaait… are these the apes you told me you tried to mind-control?”
Sunset nodded.
Trixie furrowed her brow briefly, but then shrugged. “Eh, fair enough. I’ve seen enough crazy stuff that I no longer question this sort of thing. But why would your medication cause you trouble?”
“Indeed, this question came to my mind as well,” said Luna. “I am appalled that Celestia would recommend it to me if there should be any cause for worry.”
Sunset scratched her forehead. “I forget how new this sort of thing is for you. Okay, look. The medication uses hormones to trick your body into thinking you’re pregnant, which is why you don’t go into heat. But I can’t take it, because I don’t know how magically-created hormones would affect me if they’re still in my system when I turn into a primate. And no, you don’t have to worry about it, because it’s totally safe for ponies.”
“Hmm…” Trixie rubbed her chin. “Don’t these primates have their own estrus cycles?”
“They have something similar, and their own ways of handling it. But right now, sticking a tampon up my cooter is pretty much going to do the opposite of what I’m hoping for.”
“What’s a tampon?”
“Forget it. The point is that it’s not going to work.” Sunset sighed. “If only ponies were like most animals… it would be so nice to go into heat only during the warmer months instead of all year round.”
“Ah.” Luna stared into her beer. “I am so sorry, Sunset.”
“Why? It’s not like it’s your fault.”
Luna said nothing.
“Wait…” Sunset narrowed her eyes. “Is it your fault?”
Luna chuckled nervously. “Ahaha… do you recall when I told you that there have been a great many changes since my banishment? Perhaps I might have neglected to mention that just one of those…” she sheepishly took a sip from her glass, “was the prevalence of our estrus cycles.”
“…Oh, great. I can already tell this is one of those things that’s going to require me being at least slightly drunk to handle.” Sunset rolled her eyes and began draining her nearly-full mug.
“Trixie is not comfortable with the idea that you might have messed with her mare bits!”
“Oh, no, no, no, no, no.” Luna shook her head quickly. “T’was nothing like that.”
Trixie breathed a sigh of relief.
“T’was Celestia who did it, not I.”
*PFFFFFFFFFFFFFFFFFFFFFFFFFFFFF!*
Sunset hurriedly wiped her mouth. “WHAT!?”
“That,” said Luna flatly, “was a commendable demonstration of – what do young ponies call it – a ‘spit-take’, Sunset.” She unhurriedly used several napkins to clean off the cider dripping from her face.
“Sorry,” said Sunset. “Reflex. What did you mean about Celestia changing our estrus cycles? Was it some kind of spell?”
“Nothing so dramatic.” Luna pushed the soaked napkins into a little pile to the side. “You see, in the years before my banishment, mares rarely went into heat outside of summer, late spring, and early autumn.”
“Really?” Trixie sat up, almost outraged. “That is so unfair! Have you any idea how inconvenient it is to have to regularly seek a hospital for estrus medication when you’re a travelling performer?”
“Trixie, I would remind you that a thousand years ago, mares did not have estrus medication at all. We had but a few crude spells to lessen its intensity.”
“Or even cruder spells to relieve it entirely – the other way!” Trixie giggled.
Luna sighed. “Yes, Trixie.”
“Of course, that way isn’t very effective, because you have to keep re-applying it!”
“You realize, we still had hooves for that,” Luna facehoofed. “In any case, it was commonly believed that wealthy mares were the only ones susceptible to estrus outside of the warm months, but it turns out we had missed the true cause of the problem.”
“Which was?”
Luna cleared her throat and declared, “Candles!”
“Uh, what?” Sunset blinked. “Are you saying I get horny because of hot wax? Don’t answer that question,” she said quickly, as Trixie gleefully opened her mouth to speak.
“Light, Sunset. Our bodies do not come with internal calendars. Instead, the length of the day is measured using the light that our eyes detect. Artificial lighting has confused this mechanism, making our bodies believe it is close to summer all year round. I am surprised that you did not know this already, being as studious as you are.”
“Hey, gimme a break. I was just a filly when I ran away, and haven’t been back until recently. I did a little basic research when I had my first heat, but all this is like, ancient history.”
“Fair enough, I suppose,” said Luna. “Regardless, I am sure you are aware that ponies used to sleep early to save on precious firewood. Minotaurs invented the candle and wick, but because ponies of course prefer not to involve animal fat in its manufacture, the use of acceptable substitutes made them expensive, and hence a luxury until recently.”
Trixie coughed. “Uh, so why is any of this your fault, again?”
“Ah, yes.” Luna took a sip of beer. “One evening shortly after my return, I was having trouble with my estrus. I had nopony else in the palace to discuss this with, so I confided in my sister. This was very difficult, because Celestia can be rather prudish when it comes to sex-”
“Oh yeah, totally,” said Sunset.
Luna snickered softly. “Indeed. Painful as it was, Celestia explained modern developments to me. It turns out that she had, for centuries now, been affording generous subsidies to the candlemaking industry and later, the installation of street lamps in all cities. What was once a privilege for the wealthy has, through innovation and invention, become an integral part of pony life."
Slowly, Luna lowered her beer, and her smile dimmed slightly as she sighed. “But when I praised her concern for her subjects, Celestia simply laughed and shook her head.”
***
“Luna, I love my little ponies, but we have lived with darkness since the beginning of time. I don’t raise taxes to fund programs we can easily live without.”
“Then why?”
Celestia’s horn glowed, and the nearby window opened.
The moon shone overhead, dimly illuminating the winding streets of Canterlot City. Across those streets were hundreds upon hundreds of brightly lit windows, shining with the fires of candles and lamps within.
And with that light came the unmistakable sounds of reverie and laughter, even at the late hour – bars and theaters and clubs and parties ringing their joy through the darkness. Luna could make out a crowd of ponies gathered outside a concert hall, chatting away enthusiastically about the music. A dozen couples lay on the grass of the city park, pointing out the stars in the sky. Distant, thrilled shrieks come from a colorfully-lit fairground ride, melded with excited voices of young foals playing carnival games.
Beneath the two alicorns, the city sang with life, a multitude of ponies relishing, carousing and socializing through the glory and serenity of the night.
***
“She did it for me.” Luna wiped away a happy tear. “She did it so that when I returned, I would find a world where ponies loved my night as much as her day.”
The other two were silent.
“Wow,” said Sunset at last. “That… that was nice of her.” She leaned back in her seat and let out a long sigh. “I forget she can be really thoughtful… sometimes.”
Trixie slowly came out of her deep thought. “Uh, I have a question.”
Luna looked up. “Yes?”
“If sunlight is what makes us go into heat, and if you are the pony ultimately responsible for our nightlife… does this make Celestia the matron alicorn of sex and you the matron alicorn of booze?”
Sunset groaned and rolled her eyes, but Luna simply looked at Trixie, stony faced.
Eventually, she spoke.
“Yes, Trixie. Yes, it does.”