I recently started cycling in my old town, I viewed a old bell tree forum post, which was said to be fool proof and a ton of people had backed it up and said it worked.
On the day a villager is in boxes, save and quit, load up the game, change the time and advance the year by one.
Save and quit, load up your game again,change the time, advance the year by one again.
Save and quit, load up your game, change the time, but only advance by five days
This method is said to be fool proof but, when I tried it, at least 4 times, no one was in boxes when I advanced by five days. To be safe I TT'd by one day, and eventually 2 days later, someone was in boxes. Not sure if this is because of an update or something but instead of advancing by five days like everyone else, I have to advance by seven days.