dhtmlxgantt change task estimation not working

Hello,
I have some troubles with method setEST(startDate) of GanttTask object.
Code looks like this

var project = ganttChartControl.getProjectById(ProjectId);
var tsc=project.getTaskById(TaskId);
var estD=new Date(2010,0,29);
tsc.setEST(estD);
tsc.setDuration(DurationInHours);
tsc.setName(TaskName);
tsc.setPercentCompleted(TaskPercentCompleted);
tsc.setPredecessor(TaskPredecessorTaskId);

and everything in this code works fine except setEST. Duration and percentCompleted changes excellent. But there are no errors in chart and no changes with EST.
May be I do something wrong? Has anybody used it?