Date fields seem to be limited to year (yyyy). Previously dates could have month and date as well (yyyy-mm-dd). When I'm editing a track that has the full date as part of it's tags, that date is being truncated to the year only, even if I'm only changing an unrelated field like genre.
That sounds like a critical bug. Can you please contact us through a support ticket and send us an example file that has date in it and we will have a look at it.