atldotnet: `Track.Date` does not work with iTunes (maybe also `Track.Description`?)

The problem

I recently came across a problem with setting the Recording Date (©day) via Track.Date - the track is saved, but it does not show up in iTunes.

After some experiments, I tried the following piece of code:

        var d = DateTime.Parse("2020-01-31");
// does not show up in iTunes
        var t = new Track(
            "Santa Claus_atldotnet.mp4");
        t.Date = d;
        t.Save();
        
// shows up in iTunes
        var t2 = new Track(
            "Santa Claus_atldotnet_af.mp4");
        t2.AdditionalFields["©day"] = d.ToString("yyyy-MM-dd");
        t2.Save();
        return 0;

Where the Track.AdditionalFields part shows up in iTunes, but the Track.Date does not.

Unfortunately, this is not an acceptable workaround, because

• writing ©day to AdditionalFields sometimes KILLS every other existing entry in AdditionalFields (maybe due to the fact that ©day is already mapped via Track.Date)
• or does not store the date correctly (e.g. 2020-01-31 is stored as 2020-01-01)
• or if it has been stored like this once, is completely ignored (AdditionalFields never shows up ©day, because it is already mapped to Date - this might also be the case for other mapped fields)

Another tool (mp4v2) also then reports that there are multiple ©day fields and that the file is bogus.

I’m gonna attach 4 files for experiments:

1. Original (without ©day) - Santa Claus_noday.mp4
2. Track.Date variant that does not work with iTunes - Santa Claus_atldotnet.mp4
3. AdditionalFields variant, that does work but has side effects - Santa Claus_atldotnet_af.mp4
4. mp4tags (mp4v2) variant, tagged with a tool that works like expected - Santa Claus_mp4tags.mp4

Hope you can work with these? Thanks