Yes, it is possible to adopt villagers from other towns, if you have 9 villagers or less. You just have to visit the other town and talk to the villager, when they are all boxed up.
You are able to travel in time, but be careful! You can use the in-game clock or the other clock(the one that manages the time overall on the DS), but the in-game one is easiest. You just go ahead and change the date a few days ahead. But if you are not sure when your villager is moving, you should be careful.
There are different methods to get villagers to move. I'm using one where I go back and forth. I start by starting my game and walk around till someone pings. I have to make sure that no one is leaving. Then I'll go ahead 2-3 days and check again. As soon as someone wants to move I either let them move or make them stay. If I make them stay, I'll go 5-6 days ahead and check again. If that doesn't work, then I'll go back to the original date.
Going back in time only counts as one day, no matter how many days/years you go back.