My girlfriend and I made a server earlier this morning to celebrate the release of The Wild Update. We make a new server every major update for our friends so we did the same here and leveled a lot of spawn to create a hub for our friends. This was at about 1-5 we did this. We got back on around 7:30 and everything we had done in that time span was completely undone. The world had been saved and we all left the server at 5pm. The entire server is completely reset and we all spawned back at spawn with a map and no tools, and the hill we'd removed was back again.