DATE and RELEASETIME(and also albumartist)

There are a few artists with studio albums that are released in the same year. With those artists, the order of the albums always messes up. I use Winamp on my PC and Poweramp on my phone to listen to music. So I've noticed two fields that are about the date the album got released.
DATE, and RELEASETIME. RELEASETIME was not in mp3tag itself, but I read that it works if you just put it in.

However, what should I type in both of those to make it work for both poweramp and winamp?
For example, i have steppenwolf- steppenwolf and steppenwolf- the second,
both are released in 1968, but the frist is released in january and the second in october.
When I look it up people suggest YYYY-MM-DD, but from some albums I have where the date field is already filled in, it shows no -. it just shows numbers, in a different order.

my other question is the tag albumartist.
What exactly does it mean?
If I fil lalbumartist in correctly, will I be able to put multiple artists on a song, but make it still show up in the same album? is that's what it's for? I'm not sure.

My last question is original artist and original album.
Does this mean that if I have a cover of a song, I can put the original artist in there?

edit: Is the publisher tag the record label? What is the tag used for producer, if there is any?

See for available fields.
I can see not DATE field there. I can see only YEAR (which may be mapped to TDAT).
Most players only check the 4-digit YEAR, so any extension to YEAR would probably not work.
Instead you should think of an amendment to the album title like "January edition" or "Autumn Release"
The albumartist has been introduced with V2 tags and allows just that what you described. For albums from just one artist you should put the same name in ARTIST and ALBUMARTIST. For compilations use Various Artists (or any other fancy name) for ALBUMARTIST and the real artist's name for ARTIST.

Thanks for the explenation.