How does Mp3Tag map ID3v2.3 frames?

Where can I find a complete list of how Mp3Tag maps the frames to the field names used on-screen?
i.e. in Mp3Tag there is a column field named 'Date', but it's impossible to tell exactly which frame this is http://id3.org/id3v2.4.0-frames
How Mp3Tag reads year from correctly formated TYER, TDRC or TDRL tags. If you have both TDRC and TDRL, which one is read by Mp3Tag?

see http://help.mp3tag.de/main_tags.html