Web Service Methods, Date Field Parameter for Second Ticket

I am working on a work flow that will create tickets based off of information in the original ticket. One of the fields that i would like to be brought over to the new tickets from the original ticket is the "Employee Start Date". However when I run the flow with the parameter and body as defined below The workflow fails at the webservice ticket creation step. If i remove the Date parameter from the body, and from the defined parameters list, I am able to execute the workflow with the missing field.

The parameter is defined as follows:

Name = StartDate, Data Type = Date, Source = From ticket, Source Property = Employee Start Date 

The Body is defined as follows:

{
"TypeID":1635,
"FormID":8277,
"Title":"New Employee needs Shared Email and Okta Tile Assignment {{StartDate}}",
"Description":"Created from ticket {{OrigTicketID}}",
"AccountID":{{AcctDeptID}},
"SourceID":134,
"StatusID":1271,
"PriorityID":471,
"RequestorUID":"{{RequestorUID}}",
"Attributes":
  [
    { "Name": "New Employee Name", "ID": 18624, "Value": "{{NewEmpName}}" },
    { "Name": "Skidmore Email Address", "ID": 18623, "Value": "{{SkidEmail}}" },
    { "Name": "Employee Start Date", "ID": 18621, "Value": "{{StartDate}}" },
  ] 
}

Is there a problem with how I have defined the date field within the parameters? or is it an issue with the body text?