Can I somehow get the access to calendar object knowing just the id of the input to which this object is linked?
There is no such a built-in feature.
You may place create calendars into an object. For example:
var calendars = {};
calendars[‘cInput1’] = new dhtmlxCalendarObject(‘cInput1’);
calendars[‘cInput2’] = new dhtmlxCalendarObject(‘cInput2’);
And then you get the necessary calendar by calendars[inputId].