Tidy up implementation of #15010

activesupport/lib/active_support/values/time_zone.rb

@@ -291,16 +291,10 @@ def parse(str, now=now())
       parts = Date._parse(str, false)
       return if parts.empty?
 
-      default_mday = if parts[:year] || parts[:mon]
-        1
-      else
-        now.day
-      end
-
       time = Time.new(
         parts.fetch(:year, now.year),
         parts.fetch(:mon, now.month),
-        parts.fetch(:mday, default_mday),
+        parts.fetch(:mday, parts[:year] || parts[:mon] ? 1 : now.day),
         parts.fetch(:hour, 0),
         parts.fetch(:min, 0),
         parts.fetch(:sec, 0) + parts.fetch(:sec_fraction, 0),

activesupport/test/time_zone_test.rb

@@ -255,10 +255,12 @@ def test_parse_with_incomplete_date
   end
 
   def test_parse_with_day_omitted
-    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
-    zone.stubs(:now).returns zone.local(1999, 12, 31)
-    twz = zone.parse('Feb')
-    assert_equal Time.utc(1999, 2, 1), twz.time
+    with_env_tz 'US/Eastern' do
+      zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+      assert_equal Time.local(2000, 2, 1), zone.parse('Feb', Time.local(2000, 1, 1))
+      assert_equal Time.local(2005, 2, 1), zone.parse('Feb 2005', Time.local(2000, 1, 1))
+      assert_equal Time.local(2005, 2, 2), zone.parse('2 Feb 2005', Time.local(2000, 1, 1))
+    end
   end
 
   def test_parse_should_not_black_out_system_timezone_dst_jump