Please help me with writing request for change task details: "scheduled_end_time" и "scheduled_start_time"

I try to write like this:

http://ServerName:8080/api/v3/tasks/15?format=json&TECHNICIAN_KEY=***&INPUT_DATA={"task": {"title":"TaskName","status": {"name": "Open"},"scheduled_start_time":{"value":1529989200000},"scheduled_end_time":{"value":1529992800000}}}

But the task (№15 ) is not changing, but a new task with the specified dates is created

How to change an existing task, and not create a new one?