diff --git a/ChangeLog b/ChangeLog
index 68d159cc8e..fe0d066f47 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Sep 17 00:36:01 2009  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (time_mdump): error message refined.
+
 Wed Sep 16 19:27:43 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* test/ruby/test_thread.rb (TestThread#test_recursive): remove
diff --git a/time.c b/time.c
index b12dbdcc52..29f448717e 100644
--- a/time.c
+++ b/time.c
@@ -3587,7 +3587,7 @@ time_mdump(VALUE time)
     if (FIXNUM_P(vtm.year)) {
         year = FIX2LONG(vtm.year);
         if (year < 1900 || 1900+0xffff < year)
-            rb_raise(rb_eArgError, "year too big to marshal: %ld", year);
+            rb_raise(rb_eArgError, "year too big to marshal: %ld UTC", year);
     }
     else {
         rb_raise(rb_eArgError, "year too big to marshal");