@Background Pony #32D8  
Most likely the Royal Sisters can still protect Equestria.  
Since they lost their connection to the Elements due to the NMM mess and look how things went for the sisters due to that, they were absolute failures without the Elements there.

… girl or boy will do the same if use a time machine but in equestria change the past like stop Luna of become Nightmare moon will create big problem, like Twilight and her Friends will never be friends and be safe equestria! Remember what Starlight a done and the mess a create? so change a even of the past who is 1000 years will create more damage, even is for the good of the two sister, sure your action is noble but the damage is not, why you think Celestia a not use time travel to stop Luna to be Nightmare moon or warning her past self to do something to make sure Luna not get jealous, she know the Damage of Time travel!

Truth be told, most if not all of us would do the last one.

@Background Pony #8A9C  
Not unless Twilight still wants to become Celestia’s student and ends up hatching Spike’s egg anyway.

@JP  
Spike naively commits suicide via time paradox…

Loving Spike helping Luna out there.

@Shritistrang  
Goes like this.
 
Imagine you want to go back in time to stop an embarrassing thing from happening to yourself. So you go back and prevent it. Now there is a paradox; if the embarrassing thing never happened, how do you know to undo it?
 
Thus, you instead have made a new timeline where you never did the embarrassing thing, but YOUR timeline still has you having done the embarrassing thing.

@neo4812  
Yay for basic Multiverse theory!

I would say Spiluna in the air but I can’t.

We need a tag for the boys vs girls time machine meme sometime soon.

@neo4812  
I don’t know much about Dragon Ball time travel, but yup to the second one.

@Shritistrang  
basically dragon ball z/avengers endgame time travel logic

@JP  
No, it won’t change anything from his own timeline. It will just create a new, seperate timeline where Luna doesn’t turn into Nightmare Moon.

if i had a time machine i would by some rare comics and bring them back to my time and rare movies too

Spike, that change is too much. If Luna never goes Nightmare, Celestia won’t banish her and the long chain of events that leads to her meeting Twilight Sparkle 1000 years later probably won’t happen, and Twilight never becomes Celestia’s student and the future ruler and you won’t be her advisor. In fact, your egg might not even get hatched by her (or any other pony), if it exists at all.

Luna: “Also, we see that dragons in the future abuse steroids…”