The Force Can Slow Time
This fun little theory can help explain quite a bit actually. What if places that are naturally strong in the Force or are occupied with someone incredibly strong in the Force. It could be reasoned that a planet like Dagobah that is already naturally strong in the Force coupled with the presence of one of the most powerful Jedi ever, Yoda, could actually alter time. This fact is why Luke is able to train with Yoda for a seemingly short amount of time yet learn so much from the Jedi Grand Master.