How do you set Custom field type Date using SOAP?
All date fields must be supplied in ISO 8601 at UTC-0 format as referenced under the Object Model > Object Model Overview > Primitive Data Types within the Oracle RightNow Connect Web Services for SOAP documentation.
Here is a helpful link that describes the ISO 8601 date and time format.
NOTE: Datetime fields with timezone offset are not valid within MySQL. Therefore such format is not permitted for use with ROQL when using the Connect PHP API.
Incorrect format: 2016-01-01T16:00:00-05:00
Correct format: 2016-01-01T21:00:00Z