personally, i've never time traveled (tempted to for this rock garden though, holy moly) but i've read that a few glitches can occur due to it. a forum on reddit i read had a user who lost one of their villagers unexpectedly; they just started their move process and they attempted to time travel to prevent that from happening. the villager disappeared entirely, and then when they found them again, their entire relationship had been wiped back down to 0. other than that, i haven't read too much about consequences, other than the usual memes of skipping forward.
if you do end up doing such a big skip, would be interesting to see your results and if it goes smoothly.