When editing out full date in Year to only year it still shows full date in Foobar Date. Or sometimes it shows just year in Year and full date appears in Foobar Date. Annoying...
Is this just a statement showing your opinion?
Is this a question about Foobar functions?
What do you think MP3tag can do about your problem?
Real examples would shed a lot more light on the case then, preferably with screenshots.
Could you please show us the screenshot of the extended tags dialogue Alt-T for this file?
Looks to me like the data is displayed equally in both programs
Check your collection for files that have the fields YEAR and DATE.
And also see whether you have files with APE tags but for which you do not update the APE tags.
Foobar puts the values of YEAR (TYER) and DATE (TDAT) together into 1 field.
Do you save your changes?
CTRL-S or 
or Menue File -> Save Tag
yes, at this point before I change in mp3tag
And now it would interesting to see the result after the change - a selected single file is better as the extended tags dialogue then also shows tag version information.
And what could be the pattern for this "sometimes"?
Could you check
and then see if these are the files in which Foobar shows more than you want.
OK, I only use mp3 in the library and use mp3tag to organize/edit tags.
FairStars Audio Converter Pro for converting FLAC/APE...to mp3...
So mp3tag doesn't deal with all the date tags?
How do you get that idea?
What was the result of the check for the DATE field?
Use a filter
%date% PRESENT
and if there are any files in the file list, then check in Foobar if these are the files which show more than you want
I can't see any other place to edit the "Year" in mp3tag and still end up with the full date...
I'll have to get back on the check with an album that get the problem...
The problem is: There are several fields that deal with dates. YEAR is a 4-digit-field for the year only. It would be interesting, which program wrote an invalid date format into this field. YEAR in MP3tag maps to the TYER token in MP3 files
But that may be as it is.
Then there is the field DATE in MP3tag which maps to the TDAT token in MP3 files.
Foobar has the speciality to show a field with the label Date that features the data from TYER plus (if present) the data from TDAT - all in 1 line.
So it would no be up to you to investigate if files have 2 separate fields (YEAR and DATE) in MP3tag which is then shown as just 1 field in Foobar.
So far your screenshots have not yet shown any file(s) in which the displayed times differ and whether the DATE field is present in those files.
If you want to see also the DATE field im MP3tag, customize your tag panel and/or the file list and add an object to show that data.
So I have to check with Alt-T and edit date/year there to be safe...
Is this the proof for above statement?