So you are using the Broker package. I see.
Because the StringToDate receives a string representation of the date in SHORT format and returns a Date object , maybe you can run this in reverse and see what the service expects?
Try running wm.enterprise.BuiltInUtil:DateToString. This service takes a Date object as an input. You can create one using a Java service. If you need help with this, let me know.
By the way, is setting the date field within the Broker environment an option or do you need to get it from within IS?
#Flow-and-Java-services#webMethods#Integration-Server-and-ESB