diff --git a/ChangeLog b/ChangeLog
index 92c33bb6c4..7d702cc9d0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Apr 11 10:59:58 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (append_cppflags, append_cflags, append_ldflags):
+	  utility methods to append compiler options.
+
 Sat Apr 11 08:22:24 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* lib/rdoc/text.rb: removed duplicated code.
diff --git a/ext/date/extconf.rb b/ext/date/extconf.rb
index 6f479eaa26..a0c30fa948 100644
--- a/ext/date/extconf.rb
+++ b/ext/date/extconf.rb
@@ -1,5 +1,3 @@
 require 'mkmf'
-if try_cflags("-std=iso9899:1999")
-  $CFLAGS += " " << "-std=iso9899:1999"
-end
+append_cflags("-std=iso9899:1999")
 create_makefile('date_core')
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 014e7ed53b..8a21666b76 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -613,6 +613,16 @@ MSG
     try_header(MAIN_DOES_NOTHING, flags, {:werror => true}.update(opts))
   end
 
+  def append_cppflags(flags, *opts)
+    Array(flags).each do |flag|
+      if checking_for "whether #{flag} is accepted as CPPFLAGS" {
+           try_cppflags(flag, *opts)
+         }
+        $CPPFLAGS << " " << flag
+      end
+    end
+  end
+
   def with_cflags(flags)
     cflags = $CFLAGS
     $CFLAGS = flags
@@ -625,6 +635,16 @@ MSG
     try_compile(MAIN_DOES_NOTHING, flags, {:werror => true}.update(opts))
   end
 
+  def append_cflags(flags, *opts)
+    Array(flags).each do |flag|
+      if checking_for "whether #{flag} is accepted as CFLAGS" {
+           try_cflags(flag, *opts)
+         }
+        $CFLAGS << " " << flag
+      end
+    end
+  end
+
   def with_ldflags(flags)
     ldflags = $LDFLAGS
     $LDFLAGS = flags
@@ -637,6 +657,16 @@ MSG
     try_link(MAIN_DOES_NOTHING, flags, {:werror => true}.update(opts))
   end
 
+  def append_ldflags(flags, *opts)
+    Array(flags).each do |flag|
+      if checking_for "whether #{flag} is accepted as LDFLAGS" {
+           try_ldflags(flag, *opts)
+         }
+        $LDFLAGS << " " << flag
+      end
+    end
+  end
+
   def try_static_assert(expr, headers = nil, opt = "", &b)
     headers = cpp_include(headers)
     try_compile(<<SRC, opt, &b)