diff --git a/api/js/etemplate/Et2Checkbox/Et2Checkbox.ts b/api/js/etemplate/Et2Checkbox/Et2Checkbox.ts
index 8e6460c42b..0b4c6693c7 100644
--- a/api/js/etemplate/Et2Checkbox/Et2Checkbox.ts
+++ b/api/js/etemplate/Et2Checkbox/Et2Checkbox.ts
@@ -14,6 +14,7 @@ import {Et2InputWidget} from "../Et2InputWidget/Et2InputWidget";
 import '../Et2Image/Et2Image';
 import {SlCheckbox} from "@shoelace-style/shoelace";
 import shoelace from "../Styles/shoelace";
+import {property} from "lit/decorators/property.js";
 
 export class Et2Checkbox extends Et2InputWidget(SlCheckbox)
 {
@@ -59,31 +60,21 @@ export class Et2Checkbox extends Et2InputWidget(SlCheckbox)
 		];
 	}
 
-	static get properties()
-	{
-		return {
-			...super.properties,
-			/* Different value when checked */
-			selectedValue: {type: String},
-			/* Different value when unchecked */
-			unselectedValue: {type: String}
-		}
-	}
+	@property({type: String})
+	selectedValue = 'true';
+	@property({type: String})
+	unselectedValue = '';
 
 	constructor()
 	{
 		super();
 
 		this.isSlComponent = true;
-
-		this.selectedValue = 'true';
-		this.unselectedValue = '';
 	}
 
 	connectedCallback()
 	{
 		super.connectedCallback();
-
 	}
 
 	get label()
diff --git a/api/js/etemplate/et2_core_widget.ts b/api/js/etemplate/et2_core_widget.ts
index 8f0d1c6f7d..b87d0e7b13 100644
--- a/api/js/etemplate/et2_core_widget.ts
+++ b/api/js/etemplate/et2_core_widget.ts
@@ -22,7 +22,7 @@ import {egw, IegwAppLocal} from "../jsapi/egw_global";
 import {et2_cloneObject, et2_csvSplit} from "./et2_core_common";
 import {et2_compileLegacyJS} from "./et2_core_legacyJSFunctions";
 import {et2_IDOMNode, et2_IInputNode} from "./et2_core_interfaces";
-import {loadWebComponent} from "./Et2Widget/Et2Widget";
+import {loadWebComponent,Et2Widget} from "./Et2Widget/Et2Widget";
 // fixing circular dependencies by only importing type
 import type {et2_container} from "./et2_core_baseWidget";
 import type {et2_inputWidget} from "./et2_core_inputWidget";
@@ -460,7 +460,7 @@ export class et2_widget extends ClassWithAttributes
 	 *
 	 * @param _id is the id you're searching for
 	 */
-	getWidgetById(_id): et2_widget | null
+	getWidgetById(_id): Et2Widget | et2_widget | null
 	{
 		if (this.id == _id)
 		{
@@ -480,7 +480,7 @@ export class et2_widget extends ClassWithAttributes
 		if (this.id && _id.indexOf('[') > -1 && this._children.length)
 		{
 			var ids = (new et2_arrayMgr()).explodeKey(_id);
-			var widget: et2_widget = this;
+			var widget: Et2Widget | et2_widget = this;
 			for (var i = 0; i < ids.length && widget !== null; i++)
 			{
 				widget = widget.getWidgetById(ids[i]);
diff --git a/calendar/js/app.ts b/calendar/js/app.ts
index 4ec218d0e8..b714da75b1 100644
--- a/calendar/js/app.ts
+++ b/calendar/js/app.ts
@@ -37,14 +37,11 @@ import {et2_selectbox} from "../../api/js/etemplate/et2_widget_selectbox";
 import {et2_widget} from "../../api/js/etemplate/et2_core_widget";
 import {et2_nextmatch} from "../../api/js/etemplate/et2_extension_nextmatch";
 import {et2_iframe} from "../../api/js/etemplate/et2_widget_iframe";
-// @ts-ignore
-import {date} from "../../api/js/etemplate/lib/date.js";
 import {sprintf} from "../../api/js/egw_action/egw_action_common";
 import {egw_registerGlobalShortcut, egw_unregisterGlobalShortcut} from "../../api/js/egw_action/egw_keymanager";
 import {egw, egw_getFramework} from "../../api/js/jsapi/egw_global";
 import {et2_number} from "../../api/js/etemplate/et2_widget_number";
 import {et2_template} from "../../api/js/etemplate/et2_widget_template";
-import {et2_checkbox} from "../../api/js/etemplate/et2_widget_checkbox";
 import {et2_grid} from "../../api/js/etemplate/et2_widget_grid";
 import {Et2Textbox} from "../../api/js/etemplate/Et2Textbox/Et2Textbox";
 import "./SidemenuDate";
@@ -59,6 +56,7 @@ import {et2_IInput} from "../../api/js/etemplate/et2_core_interfaces";
 import {Et2DateTime} from "../../api/js/etemplate/Et2Date/Et2DateTime";
 import {Et2Select} from "../../api/js/etemplate/Et2Select/Et2Select";
 import type {SelectOption} from "../../api/js/etemplate/Et2Select/FindSelectOptions";
+import type {Et2Checkbox} from "../../api/js/etemplate/Et2Checkbox/Et2Checkbox";
 
 /**
  * UI for calendar
@@ -2245,14 +2243,14 @@ export class CalendarApp extends EgwApp
 	 */
 	move_edit_series(_DOM,_button)
 	{
-		var content : any = this.et2.getArrayMgr('content').data;
-		var start_date = this.et2.getValueById('start');
-		var end_date = this.et2.getValueById('end');
-		var whole_day = <et2_checkbox> this.et2.getWidgetById('whole_day');
-		var duration = ''+this.et2.getValueById('duration');
-		var is_whole_day = whole_day && whole_day.value == whole_day.selected_value;
-		var button = _button;
-		var that = this;
+		const content : any = this.et2.getArrayMgr('content').data;
+		const start_date = this.et2.getValueById('start');
+		const end_date = this.et2.getValueById('end');
+		const whole_day = <Et2Checkbox>this.et2.getWidgetById('whole_day');
+		const duration = ''+this.et2.getValueById('duration');
+		const is_whole_day = whole_day && whole_day.value == whole_day.selectedValue;
+		const button = _button;
+		const that = this;
 
 		let instance_date_regex = window.location.search.match(/date=(\d{4}-\d{2}-\d{2}(?:.+Z)?)/);
 		let instance_date;
@@ -4246,7 +4244,7 @@ export class CalendarApp extends EgwApp
 		{
 			if (content.grid[i] != null)
 			{
-				checkbox = <et2_checkbox> this.et2.getWidgetById(i+'[enable]');
+				checkbox = <Et2Checkbox>this.et2.getWidgetById(i+'[enable]');
 				if (checkbox)
 				{
 					checkbox.set_value(_widget.checked);
@@ -4284,7 +4282,7 @@ export class CalendarApp extends EgwApp
 	 */
 	public videoconferenceOnChange(event)
 	{
-		let widget = <et2_checkbox> this.et2.getWidgetById('videoconference');
+		let widget = <Et2Checkbox>this.et2.getWidgetById('videoconference');
 
 		if (widget && widget.get_value())
 		{