year is currently a mandatory field for publications. Unfortunately this forces the use of a workaround to populate this field when it is not known (for such an entry see e.g.: http://bowvalleycollege.libguides.com/c.php?g=494959&p=3386873#s-lg-box-wrapper-13322180).
True, a user could entry in this case
n.d.(no date) to indicate that the date is not known, but that requires that the user is acquainted with the final style in which the entry should be rendered. This (
n.d.) is the case in APA in English, but if we resort to the locale translations, we see that the user should input
o.J. for Germany entries…
I don’t know how other styles deal with missing dates, and that is the point: the user shouldn’t care. It should be possible to leave the year field empty.