diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index 0059898ebfe19..28bc06f103ca1 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -271,7 +271,12 @@ def parse(str, now=now)
       date_parts = Date._parse(str)
       return if date_parts.empty?
       time = Time.parse(str, now) rescue DateTime.parse(str)
+
       if date_parts[:offset].nil?
+        if date_parts[:hour] && time.hour != date_parts[:hour]
+          time = DateTime.parse(str)
+        end
+
         ActiveSupport::TimeWithZone.new(nil, self, time)
       else
         time.in_time_zone(self)
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index d14d01dc30390..b9434489bb615 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -203,6 +203,24 @@ def test_parse_with_incomplete_date
     assert_equal Time.utc(1999,12,31,19), twz.time
   end
 
+  def test_parse_should_not_black_out_system_timezone_dst_jump
+    zone = ActiveSupport::TimeZone['Pacific Time (US & Canada)']
+    zone.stubs(:now).returns(zone.now)
+    Time.stubs(:parse).with('2012-03-25 03:29', zone.now).
+                       returns(Time.local(0,29,4,25,3,2012,nil,nil,true,"+03:00"))
+    twz = zone.parse('2012-03-25 03:29')
+    assert_equal [0, 29, 3, 25, 3, 2012], twz.to_a[0,6]
+  end
+
+  def test_parse_should_black_out_app_timezone_dst_jump
+    zone = ActiveSupport::TimeZone['Pacific Time (US & Canada)']
+    zone.stubs(:now).returns(zone.now)
+    Time.stubs(:parse).with('2012-03-11 02:29', zone.now).
+                       returns(Time.local(0,29,2,11,3,2012,nil,nil,false,"+02:00"))
+    twz = zone.parse('2012-03-11 02:29')
+    assert_equal [0, 29, 3, 11, 3, 2012], twz.to_a[0,6]
+  end
+
   def test_utc_offset_lazy_loaded_from_tzinfo_when_not_passed_in_to_initialize
     tzinfo = TZInfo::Timezone.get('America/New_York')
     zone = ActiveSupport::TimeZone.create(tzinfo.name, nil, tzinfo)