Not able to set Due Date while creating a ticket through https://support.zoho.com/support/WebToCase

Not able to set Due Date while creating a ticket through https://support.zoho.com/support/WebToCase

I am trying to create Ticket using  https://support.zoho.com/support/WebToCase url posting the data through multipart form request, but the due date never changes.

All i want is to set the Due date 3 days ahead of the current date.

May be I am passing the date in wrong format. I tried using the below formats: 
1. MM/dd/yyyy
2.MMM d, yyyy HH:mm:ss a
3. MM-dd-yyyy

Status for now: Everytime i create a ticket , the due Date is set to 2 days ahead of current date.(Is this default setting??)

Please help me on this to get fixed.