DatePicker: update week when value changes

packages/date-picker/src/panel/date.vue

@@ -183,6 +183,7 @@
       date(newVal) {
         this.year = newVal.getFullYear();
         this.month = newVal.getMonth();
+        if (this.selectionMode === 'week') this.week = getWeekNumber(newVal);
       }
     },