DatePicker: guards common but incorrect usage (#11673)

packages/date-picker/src/picker.vue

@@ -508,12 +508,21 @@ export default {
     },
 
     parsedValue() {
-      const isParsed = isDateObject(this.value) || (Array.isArray(this.value) && this.value.every(isDateObject));
-      if (this.valueFormat && !isParsed) {
-        return parseAsFormatAndType(this.value, this.valueFormat, this.type, this.rangeSeparator) || this.value;
-      } else {
+      if (!this.value) return this.value; // component value is not set
+      if (this.type === 'time-select') return this.value; // time-select does not require parsing, this might change in next major version
+
+      const valueIsDateObject = isDateObject(this.value) || (Array.isArray(this.value) && this.value.every(isDateObject));
+      if (valueIsDateObject) {
         return this.value;
       }
+
+      if (this.valueFormat) {
+        return parseAsFormatAndType(this.value, this.valueFormat, this.type, this.rangeSeparator) || this.value;
+      }
+
+      // NOTE: deal with common but incorrect usage, should remove in next major version
+      // user might provide string / timestamp without value-format, coerce them into date (or array of date)
+      return Array.isArray(this.value) ? this.value.map(val => new Date(val)) : new Date(this.value);
     },
 
     _elFormItemSize() {