Make `Time.zone.parse` to work with JavaScript date strings

Chrome, Safari and Firefox serialize Date objects to strings such
as 'Mon May 28 2012 00:00:00 GMT-0700 (PDT)'. When these strings
are parsed the zone is interpreted as 'GMT-0700' which doesn't
exist in the TzInfo list of timezones.

By taking advantage of the improved date/time handling in 1.9.3
we can use `Date._parse` and the `:offset` value which is parsed
correctly.

Three tests were amended to make them pass:

1.  test_parse_with_old_date

    This needed changing to a different value because the original
    value was before EST was adopted so was being changed to a
    LMT (Local Mean Time) value after the change. It didn't before
    because `DateTime` just has offsets from UTC not timezones.

2.  test_parse_should_not_black_out_system_timezone_dst_jump

    Changed the implementation of this test as the stubs were
    dependent on internal implementation details of the test.
    Confirmed that the modified test still failed when the
    implementation of `parse` was restored to pre-#5571.

3.  test_parse_should_black_out_app_timezone_dst_jump

    Ditto.

Closes #5770.

activesupport/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   Make `Time.zone.parse` to work with JavaScript format date strings. *Andrew White*
+
 *   Add `DateTime#seconds_until_end_of_day` and `Time#seconds_until_end_of_day`
     as a complement for `seconds_from_midnight`; useful when setting expiration
     times for caches, e.g.:

activesupport/lib/active_support/values/time_zone.rb

@@ -278,18 +278,23 @@ def at(secs)
     #   Time.zone.now               # => Fri, 31 Dec 1999 14:00:00 HST -10:00
     #   Time.zone.parse('22:30:00') # => Fri, 31 Dec 1999 22:30:00 HST -10:00
     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)
+      parts = Date._parse(str, false)
+      return if parts.empty?
+
+      time = Time.new(
+        parts.fetch(:year, now.year),
+        parts.fetch(:mon, now.month),
+        parts.fetch(:mday, now.day),
+        parts.fetch(:hour, now.hour),
+        parts.fetch(:min, now.min),
+        parts.fetch(:sec, now.sec) + parts.fetch(:sec_fraction, 0),
+        parts.fetch(:offset, 0)
+      )
+
+      if parts[:offset]
+        TimeWithZone.new(time.utc, self)
       else
-        time.in_time_zone(self)
+        TimeWithZone.new(nil, self, time)
       end
     end
 

activesupport/test/time_zone_test.rb

@@ -178,8 +178,8 @@ def test_parse_string_with_timezone
 
   def test_parse_with_old_date
     zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
-    twz = zone.parse('1850-12-31 19:00:00')
-    assert_equal [0,0,19,31,12,1850], twz.to_a[0,6]
+    twz = zone.parse('1883-12-31 19:00:00')
+    assert_equal [0,0,19,31,12,1883], twz.to_a[0,6]
     assert_equal zone, twz.time_zone
   end
 
@@ -204,21 +204,25 @@ def test_parse_with_incomplete_date
   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]
+    with_env_tz('EET') do
+      zone = ActiveSupport::TimeZone['Pacific Time (US & Canada)']
+      twz = zone.parse('2012-03-25 03:29:00')
+      assert_equal [0, 29, 3, 25, 3, 2012], twz.to_a[0,6]
+    end
   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]
+    with_env_tz('EET') do
+      zone = ActiveSupport::TimeZone['Pacific Time (US & Canada)']
+      twz = zone.parse('2012-03-11 02:29:00')
+      assert_equal [0, 29, 3, 11, 3, 2012], twz.to_a[0,6]
+    end
+  end
+
+  def test_parse_with_javascript_date
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.parse("Mon May 28 2012 00:00:00 GMT-0700 (PDT)")
+    assert_equal Time.utc(2012, 5, 28, 7, 0, 0), twz.utc
   end
 
   def test_utc_offset_lazy_loaded_from_tzinfo_when_not_passed_in_to_initialize