Scheduler and datepicker (minicalendar) not synchronized

Using asp.Net webform I have placed scheduler together with the a datepicker on the same page.
C# code:
var cal = new DHTMLX.Scheduler.Controls.MiniCalendar(“dhtmlxCalendar”);// initialization
cal.Navigation = true;// configuration
Scheduler.Calendars.Add(cal);// adding to the page

The problem is that selecting a date at either the scheduler or the minicalendar does not set the same date on the other. they are like two sepearated controls.
What is wrong?