add comment and test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@20365 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 32 insertions, 2 deletions

diff --git a/lib/time.rb b/lib/time.rb
index 85c715b80b..3555571f22 100644
--- a/lib/time.rb
+++ b/lib/time.rb
@@ -84,8 +84,26 @@ class Time
     end
 
     def zone_utc?(zone)
-      # * +0000 means localtime. [RFC 2822]
-      # * GMT is a localtime abbreviation in Europe/London, etc.
+      # * +0000
+      #   In RFC 2822, +0000 indicate a time zone at Universal Time.
+      #   Europe/London is "a time zone at Universal Time" in Winter.
+      #   Europe/Lisbon is "a time zone at Universal Time" in Winter.
+      #   Atlantic/Reykjavik is "a time zone at Universal Time".
+      #   Africa/Dakar is "a time zone at Universal Time".
+      #   So +0000 is a local time such as Europe/London, etc.
+      # * GMT
+      #   GMT is used as a time zone abbreviation in Europe/London,
+      #   Africa/Dakar, etc.
+      #   So it is a local time.
+      #
+      # * -0000, -00:00
+      #   In RFC 2822, -0000 the date-time contains no information about the
+      #   local time zone.
+      #   In RFC 3339, -00:00 is used for the time in UTC is known,
+      #   but the offset to local time is unknown.
+      #   They are not appropriate for specific time zone such as
+      #   Europe/London because time zone neutral, 
+      #   So -00:00 and -0000 are treated as UTC.
       if /\A(?:-00:00|-0000|-00|UTC|Z|UT)\z/i =~ zone
         true
       else
@@ -741,6 +759,18 @@ if __FILE__ == $0
       assert_equal(true, Time.rfc2822("Sat, 01 Jan 2000 00:00:00 UTC").utc?)
     end
 
+    def test_rfc2822_utc_roundtrip_winter
+      t1 = Time.local(2008,12,1)
+      t2 = Time.rfc2822(t1.rfc2822)
+      assert_equal(t1.utc?, t2.utc?, "[ruby-dev:37126]")
+    end
+
+    def test_rfc2822_utc_roundtrip_summer
+      t1 = Time.local(2008,8,1)
+      t2 = Time.rfc2822(t1.rfc2822)
+      assert_equal(t1.utc?, t2.utc?)
+    end
+
     def test_parse_leap_second
       t = Time.utc(1998,12,31,23,59,59)
       assert_equal(t, Time.parse("Thu Dec 31 23:59:59 UTC 1998"))