diff --git test/test_time.rb test/test_time.rb
index 0a6659f..167fbbf 100644
--- test/test_time.rb
+++ test/test_time.rb
@@ -324,6 +324,11 @@ def test_zone_0000
     assert_equal(true, Time.rfc2822("Sat, 01 Jan 2000 00:00:00 -0000").utc?)
     assert_equal(false, Time.rfc2822("Sat, 01 Jan 2000 00:00:00 +0000").utc?)
     assert_equal(true, Time.rfc2822("Sat, 01 Jan 2000 00:00:00 UTC").utc?)
+    ENV['TZ'] = 'UTC'
+    assert_equal(true, Time.now.utc?)
+    ENV['TZ'] = 'Asia/Tokyo'
+    assert_equal(false, Time.now.utc?)
+    ENV['TZ'] = nil
   end
 
   def test_rfc2822_utc_roundtrip_winter
diff --git time.c time.c
index 603fe8b..85cd943 100644
--- time.c
+++ time.c
@@ -1925,6 +1925,11 @@ time_init_0(VALUE time)
     rb_timespec_now(&ts);
     tobj->timew = timespec2timew(&ts);
 
+    MAKE_TM(time, tobj);
+    if (rb_equal(tobj->vtm.utc_offset, INT2FIX(0))) {
+        tobj->gmt = 1;
+    }
+
     return time;
 }