Thought I'd share, because this process takes 15 seconds TOPS, and the shortest tutorials on Youtube for this are, what, four, maybe five minutes? Didn't want to waste your time like they do :)
1. Pause the game
2. Press: "Open to LAN"
3. Press: "Allow cheats: ON"
4. Press: "Start LAN World"
5. Enter the game world again
6. Press / to open the console
7. Type gamemode 1
8. Do whatever!
Someone on the bugtracker said this is intended behavior, oddly enough. Note that this method does NOT remove the 100 minute timer. Anyone doing that should feel bad :) Play fair, buy the game!
![](https://i.ytimg.com/vi/aIgpq23IAAQ/maxresdefault.jpg)