SAPUI5: Change date picker value

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Date Picker</title>

  <script src="https://sapui5.hana.ondemand.com/resources/sap-ui-core.js" 
		id="sap-ui-bootstrap" 
		data-sap-ui-libs="sap.m" 
		data-sap-ui-resourceroots='{"view": "./"}' 
		data-sap-ui-theme="sap_fiori_3" 
		data-sap-ui-xx-bindingSyntax="complex">
  </script>

<script>
    sap.ui.localResources("view");  //get access to view folder
    
    var app = new sap.m.App({
      initialPage: "idMain"
    });
    
    var page = sap.ui.view({
      id: "idMain",
      viewName: "view.Main",
      type: sap.ui.core.mvc.ViewType.XML
    });
    
    app.addPage(page);
    app.placeAt("content"); 
  </script>

</head>

<body class="sapUiBody" role="application">
  <div id="content"></div>
</body>

</html>

{
	"sap.app": {
		"id": "sap.m.sample.DatePicker",
		"applicationVersion": {
			"version": "1.0.0"
		}
	},
	"sap.ui5": {
		"rootView": {
			"viewName": "sap.m.sample.DatePicker.Group",
			"type": "XML",
			"async": true
		},
		"dependencies": {
			"libs": {
				"sap.ui.core": {},
				"sap.ui.layout": {},
				"sap.m": {},
				"sap.ui.unified": {}
			}
		},
		"config": {
			"sample": {
				"files": [
					"Group.view.xml",
					"Group.controller.js",
					"manifest.json"
				]
			}
		}
	}
}

sap.ui.controller("view.Main", {

  onInit: function() {
    this.oToDatePicker = this.byId("idToDate");
    this.oFromDatePicker = this.byId("idFromDate");
  },

  handleToDateNavigate: function(oEvent) {
    var oSource = oEvent.getSource();
    var sFromDate = this.oFromDatePicker.getValue();
    var oFromDate = new Date(sFromDate);
    var bFromDateValid = this.oFromDatePicker.isValidValue();

    // set selected date of date picker calendar to 'From Date' when valid
    if (bFromDateValid && sFromDate) {
      var oCalendar = oSource._getCalendar();
      oCalendar.focusDate(oFromDate);
      var oFromDateDateRange = new sap.ui.unified.DateRange()
        .setStartDate(oFromDate);
      oCalendar.insertSelectedDate(oFromDateDateRange);
    }
  },
});

<sap.ui.core.mvc:View controllerName="view.Main"
    xmlns="sap.m"
    xmlns:core="sap.ui.core"
    xmlns:sap.ui.core.mvc="sap.ui.core.mvc"
    xmlns:f="sap.ui.layout.form"
    xmlns:l="sap.ui.layout">
    <Page title="How to change default value of datepicker in runtime on a fiori-App?">
        <content>
          
        	<f:SimpleForm editable="true" width="75vw">
        	  <f:content>
        
              <Label text="From Date" />
              <DatePicker id="idFromDate" />

              <Label text="To Date" />
              <DatePicker id="idToDate" navigate="handleToDateNavigate"/>
        	  </f:content>
        	</f:SimpleForm>
        </content>
    </Page>
</sap.ui.core.mvc:View>