5 days after the time has been changed everything will return to normal.
Alternatively, a safer way of changing the time is from within the game itself.
It acts the same as if the system time was changed, but things will come back to normal after 24 hours to the next morning,
Time travel penalty
- You may not be able to get donations at the fountain.
- The shops and markets won't restock with new items.
- Seasonal items disappear from the "Seasonal" tab. (Players will still be able to buy the seasonal items in the "In Stock" tab if they already bought it.)
- If using the system clock to change the time, it may mess up other real-time games that you do not want to be affected.
- Time traveling can be considered cheating, so the cooldown time for items and such to work is probably so the feature of changing the time isn't abused by the Player.
- The term time traveling is also very common in the Animal Crossing community.