Fixing date comparison on instance.set()

lib/instance.js

@@ -339,8 +339,13 @@ Instance.prototype.set = function(key, value, options) { // testhint options:non
           }
 
           // Convert date fields to real date objects
-          if (this.Model._hasDateAttributes && this.Model._isDateAttribute(key) && value !== null && value !== undefined && !(value instanceof Date) && !value._isSequelizeMethod) {
-            value = new Date(value);
+          if (this.Model._hasDateAttributes && this.Model._isDateAttribute(key) && !!value && !value._isSequelizeMethod) {
+            if (!(value instanceof Date)) {
+              value = new Date(value);
+            }
+            if (originalValue && value.getTime() === originalValue.getTime()) {
+              return;
+            }
           }
         }
 

test/unit/instance/changed.test.js

@@ -62,6 +62,22 @@ describe(Support.getTestDialectTeaser('Instance'), function() {
       expect(user.changed('birthdate')).to.equal(true);
     });
 
+    it('should return false for two instances with same value', function () {
+      var milliseconds = 1436921941088;
+      var firstDate = new Date(milliseconds);
+      var secondDate = new Date(milliseconds);
+
+      var user = this.User.build({
+        birthdate: firstDate
+      }, {
+        isNewRecord: false,
+        raw: true
+      });
+
+      user.set('birthdate', secondDate);
+      expect(user.changed('birthdate')).to.equal(false);
+    });
+
     it('should return true for changed JSON with same object', function () {
       var user = this.User.build({
         meta: {
@@ -79,4 +95,4 @@ describe(Support.getTestDialectTeaser('Instance'), function() {
       expect(user.changed('meta')).to.equal(true);
     });
   });
-});
\ No newline at end of file
+});