DATE tag in Ogg files is misinterpreted as year.
When easytag reads an Ogg file it assigns the value of the DATE
tag to FileTag->year
(see ogg.c:947). Later the value is considered invalid if it is longer than four characters which is against the Vorbis Comment specification which defines the tag as
Date the track was recorded
easytag edits the tag automatically and drops month and year information.