you can start cycling when a villager is in boxes. this method is random, so there's no way to know which villager will be in boxes next.
Example
Pietro in boxes on March 6, 2015
Once he's adopted Time travel back 1 year and 5 days to March 1, 2014
then time travel 1 year ahead to March 1, 2015
next time travel 5 days ahead to March 6, 2015
Next villager will be in boxes
Does this make sense?