Make sure you are not opening a duplicate.

• I have searched the issue tracker and did not find an issue describing my bug.

Description of your suggestion.

The dungeon cooldown doesn't seem to progress if the entrance is in an unloaded chunk; requiring players to forceload chunks to keep the timer going is probably a bad idea.

This is right, it is not the best idea.

Changed it to use time difference with 24b48b6