http://www.movielabs.org/creativeworks/model/eidr#dateIsRequired
Property 'date is required'

DatatypeProperty

Series or Season

date is required

boolean

If true then all child records (Seasons or seasonless Episodes of a Series, Episodes of a Season) must specify a full date (xs:date) for the Release Date field. This is useful when the season-less episodes do not have a title as in a news program or soap opera. This is usually not present or false at the Series level.