If @@toStringTag is not present, use the old-school `Object#toStrin…

…g` test.

index.js

@@ -1,12 +1,20 @@
 'use strict';
 
 var getDay = Date.prototype.getDay;
-
-module.exports = function isDateObject(value) {
+var tryDateObject = function tryDateObject(value) {
 	try {
 		getDay.call(value);
 		return true;
 	} catch (e) {
 		return false;
 	}
 };
+
+var toStr = Object.prototype.toString;
+var dateClass = '[object Date]';
+var hasToStringTag = typeof Symbol === 'function' && typeof Symbol.toStringTag === 'symbol';
+
+module.exports = function isDateObject(value) {
+	if (typeof value !== 'object' || value === null) { return false; }
+	return hasToStringTag ? tryDateObject(value) : toStr.call(value) === dateClass;
+};