If the TDAT frame's contents begin with 00 (0012 for example, meaning the month but not the date is known), then foobar returns "0000" in the playlist.
It happens with any of the following title formatting:
$year(%date%)
$cut(%date%,4)
$left(%date%,4)
$substr(%date%,1,$sub($strchr(%date%,-),1))
I also tried substituting $meta(date) in those scripts.
foobar sorts the albums correctly in the playlist when you sort by year. It's just displaying the year incorrectly.
This is, of course, occurring in 1.1.13
The bug shows in the DUI as well as Facets and Columns UI. Interestingly, if you create a filter in CUI, the filter will display two years separately for tracks with the aforementioned TDAT frames: once under 0000 and once under the correct year.
EDIT:
This bug also affects $month(%date%). "00" is returned for month under the same condition as outlined above. Tracks are only listed once however in a CUI filter. This time under 00 only.