The format for dates are are using milliseconds form, for example:

{
    "request-instance-id" : 4,
    "request-status" : "QUEUED",
    "request-message" : "Ready to execute",
    "request-retries" : 3,
    "request-executions" : 0,
    "request-command" : "org.jbpm.executor.commands.PrintOutCommand",
    "request-scheduled-date" : 1455069600000
  }

The problem with this format is that it is not readable and might confuse users using other ways to communicate with the kie server than using its REST API.

The suggested solution is use a Jackson object mapper to configure the desired date format. This is better explained in this article:

http://wiki.fasterxml.com/JacksonFAQDateHandling