Not sure if this is a bug or an overlooked feature.
The date tag appears to be supported by the app as it is displayed after the artist in the library. But the date tag is not used for the Years library filter. This leaves the Years filter empty.
Years filter would become usable for formats that deprecate the year tag in favour of the date tag.
Libraries that have Vorbis comments and possibly ID3v2.4 tags would be filterable by year.
It should work, there’s different date tags and many different formats to store that date.
Please provide files that does not have the year filled.
If you’ve still got the Opus that I sent for the other issue, that has only a date set. But I’ll send another.
Both ID3v2.4 and Vorbis comments use the ISO format with optional month and date: YYYY[-MM[-DD]], so it should be easy to parse valid dates, then fall back to year if unset or unparsable. Presumably the taglib library already does this.
Just tested and all your songs have the proper year extracted.
The year library entry correspond to the albums year. If you have no albums you can use the smart filters to filter songs by years.