Socha,
You may only write queries that contain a field name on the left of the operator, and a value or date variable on the right side of the operator. For example, the query (CreationDate < AcceptedDate) is invalid, because both CreationDate and AcceptedDate are queryable fields listed in the Web Services API documentation.
You will need to enter a date in place of the Release.ReleaseDate.
More information about queries is available here:
Build App Queries | CA Agile Central Help