Hello Klaus,
Looks like that there is an issue with the format of the date/time string. See the reply to the forum post Workflow Script won’t get Local Variable Value, for example.
I got the following as result
[0002] Thu Jun 12 17:30:00 PDT 2025
When executing the following line of JScript code by the Run Script task
Watch.Log(new Date("2025/06/13T07:30:00"), 2);