iTunes has a Release Date field but you cannot actually edit the field in iTunes, at least not for music files,there is also a Year field and this is editable but sometimes it would be useful to use both.
In Jaikoz the Year field is clearly displayed in the default configuration but for mp3s the Release Date field is also available. By using View/Show ID3 and selecting the ID3 Edit tab you can see the Release Time (TDRL) field and
if you enter a value in here and save changes the
change is reflected in iTunes Release Date field.
Behind the scenes Release Time use the ID3v24 frame TDRL, whereas Year uses TDRC.