Tired of waiting for Stella to get finished doing S&M with the monsters on the dungeon.
Here's a quicker way.

Step 1: Enter any Dungeon
Step 2: Save game
Step 3: Return to title
Step 4: Change your computer clock settings depending on the amount of time the dungeon needs to finish.
Step 5: Load game
Step 6: Finish Dungeon then change back the original computer clock time
Step 7: Repeat Step 1 until you completed every dungeon available.

You're welcome I just saved your time.

*Do note that you need to do the true ending route to get all the dungeons.
Edit: Thanks for the comments below. It's much faster now. I'm editing this guide on my tablet. Currently not on my PC.