The CURRENT_TIMESTAMP datetime function returns the current date and local time in ISO8601 format.
CURRENT_TIMESTAMP returns an ISO8601 TIMESTAMP value representing the current date and local time. As with all SQL functions that take no parameters, no parentheses are required or accepted. All calls to CURRENT_TIMESTAMP within the processing of one node are guaranteed to return the same value.
<Body>
<Message>Hello World</Message>
<DateStamp>2017-06-07T11:52:21.450199+01:00</DateStamp>
</Body>
use the following ESQL:SET OutputRoot.XMLNS.Body.Message = 'Hello World';
SET OutputRoot.XMLNS.Body.DateStamp = CURRENT_TIMESTAMP;