Time Travel
From Wild World Wiki
Time Travelling is a tactic employed by some AC:WW players to speed through the game rather than playing day-by-day as regular players do. There are both some large drawbacks and great bonuses for Time Travellers, and while it isn't for everyone it is a valid way of playing.
Time Travelling is done by changing either the in-game clock (accessible from the phone in your bedroom, or when loading up your character) or by changing the DS' internal clock to a specific date.
Reasons to time-travel include growing fruit quickly, seeing events that others will not see for several months, avoiding the days when Nooks is closed, and getting extra items.
Reasons not to time-travel are that it causes your town to fill with weeds (more and more depending on how much you time travel) and possibly a Rafflesia, your townspeople will dislike you and/or leave, you will severely shorten the game's playable lifespan (if you can do all decembers events in june, you might not want to play in december), and there are possibilities that it can also affect your game adversely.