GSA doesn't like empty lists in data.json files either (revise output and amend validator)
tighten the data.json validator to require that in ISO8601 fields the date/time separator be a T and not any character
fixes for generating the date fields (issued/modified/temporal): the date/time separator must be T (ISO 8601) and not a space (Drupal), when issued/modified looks like a plain date remove the midnight time component ('T00:00:00'), don't generate temporal if we only have a Coverage Period Fiscal Year Start/End and not regular dates or if either the start or end is not set (previously we generated 'Unknown' in the output which was definitely not valid); and update the validator to include the text of invalid dates in the output