Problem by using timestamp as parameter

Hi Jasper fans,

on my jasperserver, i have a report with two timestamp parameters (StartDate, EndDate). If i want to pass the date via the restv2 interface, i receive the following error:

<errorCode>input.controls.validation.error</errorCode>

<message>Input controls validation failure</message>

The value of the timestamp parameter is just a typically sql.timestamp like: 2018-06-01 19:52:34.266

My GET-Request is like: HOST:8080/jasperserver/rest_v2/reports/myReport.pdf?StartDate=2018-06-01 19:52:34.266

I don´t know why the server rest interface throws a validation error. Does anyone have a suggestion or idea to solve this problem? Thank you very much.

Kind Regards Florian