Release Date removed from tag

I used to put the release date for mp3s in the field RELEASE DATE, but recently changed it to the RELEASETIME field, as that is the only way for it to show in iTunes (and comply with standards).
But if a tag is changed in any way in iTunes (or Winamp I found out), the RELEASETIME field is deleted. If altered in any way in foobar2000, that field is changed to RELEASE DATE again.

Can anybody tell me why this is happening, or better yet, show me a way to prevent it from happening?

Regards, Paz

P.S. I know this isn't the fault of mp3tag. But it is because of mp3tag that I can even edit the release date field, so that is why I came here to ask. Besides, this is the place where the experts reside, right?