How to use webservices api IOT devices

I got a web service API. I know basic knowledge web services. I am trying to test the web service through the postman. but I could not able to succeed. if any have answer please help me. I got sample code nodejs. below I gave web services API. please, anyone, see and how to handle that data.

POST /api/v1/sessions
Date: Wed, 28 Nov 2018 06:22:27 -0000
Content-Type: application/json;charset=utf-8
Content-MD5: wQsVzvcXwtwzoiZ13iAVWA==

{
"password": "sym", 
"username": "sym"
}

they gave their own json commander tools. if I send this request in JSON commander it is giving the proper response.if I use the same request. I tested by the postman.it is not working. and getting this error response also

{
"status" : 400,
"code" : 40001,
"resource" : null,
"properties" : [ ],
"message" : "The Date header is invalid.",
"developerMessage" : "The Date header is invalid. Make sure that a the Date or X-Aah-Date header is set and has a valid format."