Allow to clear due date (#19201)

src/components/ha-dialog-date-picker.ts

@@ -50,6 +50,15 @@ export class HaDialogDatePicker extends LitElement {
         @datepicker-value-updated=${this._valueChanged}
         .firstDayOfWeek=${this._params.firstWeekday}
       ></app-datepicker>
+      ${this._params.canClear
+        ? html`<mwc-button
+            slot="secondaryAction"
+            @click=${this._clear}
+            class="warning"
+          >
+            ${this.hass.localize("ui.dialogs.date-picker.clear")}
+          </mwc-button>`
+        : nothing}
       <mwc-button slot="secondaryAction" @click=${this._setToday}>
         ${this.hass.localize("ui.dialogs.date-picker.today")}
       </mwc-button>
@@ -66,6 +75,11 @@ export class HaDialogDatePicker extends LitElement {
     this._value = ev.detail.value;
   }
 
+  private _clear() {
+    this._params?.onChange(undefined);
+    this.closeDialog();
+  }
+
   private _setToday() {
     const today = new Date();
     this._value = format(today, "yyyy-MM-dd");