I see a lot of people saying this so I want to talk a bit more about this. If the persons behind ACNL, or whatever game for that matter, didn't want people to time travel there would be a trillion of ways to prevent this without completely taking away the change time/date-option. The makers of whatever game can have all sorts of intensions for how they want players to play it but that doesn't mean players can make those expectations true. Without proper communication and rules between maker and player this simply can't be done and it wouldn't make the game more enoyable. The fun of games nowadays is that you can use your imagination and strict rules would take that fun away.
I'm not saying with this that your current intension or though is 'wrong' as wrong is simply an opinion, I do say that the idea of changing your style of playing games just because you've the idea you need to because the game is intended to play in a different way is wrong. You should just play the game as you want it to and if game makers don't want that, they certainly will change things in the game so people can't do those things anymore.
The idea of constantly adapting to other people, people who you don't even know and don't know the intensions you're basing your discisions on is candid benevolant and if I might say a bit stupid, but that's something you may learn in the future. Accepting yourself and your actions is the most important part here.
I'm not saying this directed at you but at all people who read this. I know that sounds very pedantic, but I want to make clear that I did not forget that maybe this isn't your deeper reason of changing your playing style although you write it like that. But hey, let's not make this a word game.