It may be unrelated but I recall coming across a post in the past that mentioned that MusicBee's date format follows your system settings.
So if your system settings aren't using that date format, you may want to experiment with changing it to that.
As a last resort, I personally would use the "search and replace" tool to change them back to the desired format.
I already spend hours on end on social media. Might as well spare a few of those to a greater purpose here.