DATE vs YEAR

[ptrk.mj]

Which tags do you use? ID3v2.4, I suppose.

From my understanding DATE (TDAT) is only available with ID3v2.3 tags (the frame was discontinued in ID3v2.4). So if you try to set it Mp3tag remaps it to YEAR (TDRC) and you end up with two fields.

Mp3tag tag field mappings:
file:///C:/Program%20Files/Mp3tag/help/main_tags.html

ID3v2.4 frames:
http://www.id3.org/id3v2.4.0-frames

Edit:

YEAR is a timestamp field. You can enter the whole information in it (don't know how it works in practice with software players/portable devices, I've never tried it but Mp3tag is able to save it)

The timestamp fields are based on a subset of ISO 8601. When being as
precise as possible the format of a time string is
yyyy-MM-ddTHH:mm:ss (year, "-", month, "-", day, "T", hour (out of
24), ":", minutes, ":", seconds), but the precision may be reduced by
removing as many time indicators as wanted. Hence valid timestamps
are
yyyy, yyyy-MM, yyyy-MM-dd, yyyy-MM-ddTHH, yyyy-MM-ddTHH:mm and
yyyy-MM-ddTHH:mm:ss. All time stamps are UTC. For durations, use
the slash character as described in 8601, and for multiple non-
contiguous dates, use multiple strings, if allowed by the frame
definition.