MC stores Dates as a decimal number representing the number of days since the December 30th, 1899 at 00:00:00, which is known as the epoch date. Add an Expression Column to any View and use the Expression [Date,0] to see the raw data, which will be a decimal number. That Date number is stored in a tag called JR_DATE in a FLAC file, for example. It looks like the "Date" tag in the file just stores the Year for FLAC.
You are in complete control of how Dates are formatted for viewing in MC, but not how they are stored, and they are stored differently for different file types. You can view the plain text tag section at the beginning of a FLAC files using a decent editor, such as Notepad++. I'm not sure if you can do the same with DSF files.
Tags written to files are written in plain text, and so they would need a format. If so, on Windows, MC would follow the Windows Region Settings. You must have those set to YYYY-DD-MM. Although that doesn't even seem to be an option in Windows 10.
Of course, that is assuming that Simon is correct about the date format. Verify what Simon has said. I've never known any common system that uses YYYY-DD-MM. MC tends to follow standards pretty well, and other people are using MimimServer with MC. Maybe those others connect the MimimServer to the MC DLNA Server, rather than import the files directly. Search the forum.
