diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 11f48f9..c4d369d 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -3652,6 +3652,37 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREADS_NUM_PROCESSORS_NP], [
 ])
 
 dnl
+dnl Check whether pthread_cond_timedwaitonclock_np is available in <pthread.h> for std::condition_variable to use,
+dnl and define _GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP.
+dnl
+AC_DEFUN([GLIBCXX_CHECK_PTHREAD_COND_TIMEDWAITONCLOCK_NP], [
+
+  AC_LANG_SAVE
+  AC_LANG_CPLUSPLUS
+  ac_save_CXXFLAGS="$CXXFLAGS"
+  CXXFLAGS="$CXXFLAGS -fno-exceptions"
+  ac_save_LIBS="$LIBS"
+  LIBS="$LIBS -lpthread"
+
+  AC_MSG_CHECKING([for pthread_cond_timedwaitonclock_np])
+  AC_CACHE_VAL(glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP, [
+    GCC_TRY_COMPILE_OR_LINK(
+      [#include <pthread.h>],
+      [pthread_mutex_t mutex; pthread_cond_t cond; struct timespec ts; int n = pthread_cond_timedwaitonclock_np(&cond, &mutex, 0, &ts);],
+      [glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=yes],
+      [glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=no])
+  ])
+  if test $glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP = yes; then
+    AC_DEFINE(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP, 1, [Define if pthread_cond_timedwaitonclock_np is available in <pthread.h>.])
+  fi
+  AC_MSG_RESULT($glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP)
+
+  CXXFLAGS="$ac_save_CXXFLAGS"
+  LIBS="$ac_save_LIBS"
+  AC_LANG_RESTORE
+])
+
+dnl
 dnl Check whether sysctl is available in <pthread.h>, and define _GLIBCXX_USE_SYSCTL_HW_NCPU.
 dnl
 AC_DEFUN([GLIBCXX_CHECK_SYSCTL_HW_NCPU], [
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index 337f614..a46efd8 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -869,6 +869,9 @@
 /* Define if pthreads_num_processors_np is available in <pthread.h>. */
 #undef _GLIBCXX_USE_PTHREADS_NUM_PROCESSORS_NP
 
+/* Define if pthread_cond_timedwaitonclock_np is available in <pthread.h>. */
+#undef _GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP
+
 /* Define if POSIX read/write locks are available in <gthr.h>. */
 #undef _GLIBCXX_USE_PTHREAD_RWLOCK_T
 
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index e9521d6..19434c4 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -20220,6 +20220,89 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+# For pthread_cond_timedwaitonclock_np
+
+
+
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+  ac_save_CXXFLAGS="$CXXFLAGS"
+  CXXFLAGS="$CXXFLAGS -fno-exceptions"
+  ac_save_LIBS="$LIBS"
+  LIBS="$LIBS -lpthread"
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_cond_timedwaitonclock_np" >&5
+$as_echo_n "checking for pthread_cond_timedwaitonclock_np... " >&6; }
+  if test "${glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+
+    if test x$gcc_no_link = xyes; then
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+pthread_mutex_t mutex; pthread_cond_t cond; struct timespec ts; int n = pthread_cond_timedwaitonclock_np(&cond, &mutex, 0, &ts);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=yes
+else
+  glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+  if test x$gcc_no_link = xyes; then
+  as_fn_error "Link tests are not allowed after GCC_NO_EXECUTABLES." "$LINENO" 5
+fi
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+pthread_mutex_t mutex; pthread_cond_t cond; struct timespec ts; int n = pthread_cond_timedwaitonclock_np(&cond, &mutex, 0, &ts);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=yes
+else
+  glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+
+fi
+
+  if test $glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP = yes; then
+
+$as_echo "#define _GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP 1" >>confdefs.h
+
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP" >&5
+$as_echo "$glibcxx_cv_PTHREAD_COND_TIMEDWAITONCLOCK_NP" >&6; }
+
+  CXXFLAGS="$ac_save_CXXFLAGS"
+  LIBS="$ac_save_LIBS"
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+
 
   ac_fn_c_check_header_mongrel "$LINENO" "locale.h" "ac_cv_header_locale_h" "$ac_includes_default"
 if test "x$ac_cv_header_locale_h" = x""yes; then :
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 96ff16f..f59981c 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -218,6 +218,9 @@ GLIBCXX_ENABLE_LIBSTDCXX_TIME
 # Check for tmpnam which is obsolescent in POSIX.1-2008
 GLIBCXX_CHECK_TMPNAM
 
+# For pthread_cond_timedwaitonclock_np
+GLIBCXX_CHECK_PTHREAD_COND_TIMEDWAITONCLOCK_NP
+
 AC_LC_MESSAGES
 
 # For hardware_concurrency
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index f7da017..883af12 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -35,6 +35,7 @@
 # include <bits/c++0x_warning.h>
 #else
 
+#include <bits/c++config.h>
 #include <chrono>
 #include <mutex>
 #include <ext/concurrence.h>
@@ -63,7 +64,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   /// condition_variable
   class condition_variable
   {
-    typedef chrono::system_clock	__clock_t;
+#if defined(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP)
+    typedef chrono::steady_clock	__steady_clock_t;
+    typedef chrono::steady_clock	__best_clock_t;
+#else
+    typedef chrono::system_clock	__best_clock_t;
+#endif
+    typedef chrono::system_clock	__system_clock_t;
     typedef __gthread_cond_t		__native_type;
 
 #ifdef __GTHREAD_COND_INIT
@@ -98,10 +105,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  wait(__lock);
       }
 
+#if defined(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP)
     template<typename _Duration>
       cv_status
       wait_until(unique_lock<mutex>& __lock,
-		 const chrono::time_point<__clock_t, _Duration>& __atime)
+		 const chrono::time_point<__steady_clock_t, _Duration>& __atime)
+      { return __wait_until_impl(__lock, __atime); }
+#endif
+
+    template<typename _Duration>
+      cv_status
+      wait_until(unique_lock<mutex>& __lock,
+		 const chrono::time_point<__system_clock_t, _Duration>& __atime)
       { return __wait_until_impl(__lock, __atime); }
 
     template<typename _Clock, typename _Duration>
@@ -109,9 +124,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       wait_until(unique_lock<mutex>& __lock,
 		 const chrono::time_point<_Clock, _Duration>& __atime)
       {
-	// DR 887 - Sync unknown clock to known clock.
 	const typename _Clock::time_point __c_entry = _Clock::now();
-	const __clock_t::time_point __s_entry = __clock_t::now();
+	const __best_clock_t::time_point __s_entry = __best_clock_t::now();
 	const auto __delta = __atime - __c_entry;
 	const auto __s_atime = __s_entry + __delta;
 
@@ -134,24 +148,47 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       cv_status
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime)
-      { return wait_until(__lock, __clock_t::now() + __rtime); }
+      { return wait_until(__lock, __best_clock_t::now() + __rtime); }
 
     template<typename _Rep, typename _Period, typename _Predicate>
       bool
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime,
 	       _Predicate __p)
-      { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
+      { return wait_until(__lock, __best_clock_t::now() + __rtime, std::move(__p)); }
 
     native_handle_type
     native_handle()
     { return &_M_cond; }
 
   private:
+#if defined(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP)
+    template<typename _Dur>
+      cv_status
+      __wait_until_impl(unique_lock<mutex>& __lock,
+			const chrono::time_point<__steady_clock_t, _Dur>& __atime)
+      {
+	auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
+	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
+
+	__gthread_time_t __ts =
+	  {
+	    static_cast<std::time_t>(__s.time_since_epoch().count()),
+	    static_cast<long>(__ns.count())
+	  };
+
+	pthread_cond_timedwaitonclock_np(&_M_cond, __lock.mutex()->native_handle(),
+					 CLOCK_MONOTONIC,
+					 &__ts);
+
+	return (__steady_clock_t::now() < __atime
+		? cv_status::no_timeout : cv_status::timeout);
+      }
+#endif
     template<typename _Dur>
       cv_status
       __wait_until_impl(unique_lock<mutex>& __lock,
-			const chrono::time_point<__clock_t, _Dur>& __atime)
+			const chrono::time_point<__system_clock_t, _Dur>& __atime)
       {
 	auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
 	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
@@ -165,7 +202,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	__gthread_cond_timedwait(&_M_cond, __lock.mutex()->native_handle(),
 				 &__ts);
 
-	return (__clock_t::now() < __atime
+	return (__system_clock_t::now() < __atime
 		? cv_status::no_timeout : cv_status::timeout);
       }
   };
@@ -185,7 +222,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Like above, but mutex is not required to have try_lock.
   class condition_variable_any
   {
+#if defined(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP)
+    typedef chrono::steady_clock	__clock_t;
+#else
     typedef chrono::system_clock	__clock_t;
+#endif
     condition_variable			_M_cond;
     shared_ptr<mutex>			_M_mutex;
 
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
index 04945f1..6687e9c 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
@@ -27,6 +27,7 @@
 #include <system_error>
 #include <testsuite_hooks.h>
 
+template <typename ClockType>
 void test01()
 {
   bool test __attribute__((unused)) = true;
@@ -38,10 +39,10 @@ void test01()
       std::mutex m;
       std::unique_lock<std::mutex> l(m);
 
-      auto then = std::chrono::steady_clock::now();
+      auto then = ClockType::now();
       std::cv_status result = c1.wait_until(l, then + ms);
       VERIFY( result == std::cv_status::timeout );
-      VERIFY( (std::chrono::steady_clock::now() - then) >= ms );
+      VERIFY( (ClockType::now() - then) >= ms );
       VERIFY( l.owns_lock() );
     }
   catch (const std::system_error& e)
@@ -54,8 +55,28 @@ void test01()
     }
 }
 
+/* User defined clock that ticks in two-thousandths of a second
+   forty-two minutes ahead of steady_clock. */
+struct user_defined_clock
+{
+  typedef std::chrono::steady_clock::rep rep;
+  typedef std::ratio<1,2000> period;
+  typedef std::chrono::duration<rep, period> duration;
+  typedef std::chrono::time_point<user_defined_clock> time_point;
+
+  const bool is_steady = true;
+
+  static time_point now() noexcept
+  {
+    using namespace std::chrono;
+    return time_point(duration_cast<duration>(steady_clock::now().time_since_epoch()) + minutes(42));
+  }
+};
+
 int main()
 {
-  test01();
+  test01<std::chrono::steady_clock>();
+  test01<std::chrono::system_clock>();
+  test01<user_defined_clock>();
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable_any/members/2.cc b/libstdc++-v3/testsuite/30_threads/condition_variable_any/members/2.cc
index 75d8ac3..2b42dca 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable_any/members/2.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable_any/members/2.cc
@@ -52,6 +52,7 @@ struct Mutex
 };
 
 
+template <typename ClockType>
 void test01()
 {
   bool test __attribute__((unused)) = true;
@@ -63,10 +64,10 @@ void test01()
       Mutex m;
       m.lock();
 
-      auto then = std::chrono::steady_clock::now();
+      auto then = ClockType::now();
       std::cv_status result = c1.wait_until(m, then + ms);
       VERIFY( result == std::cv_status::timeout );
-      VERIFY( (std::chrono::steady_clock::now() - then) >= ms );
+      VERIFY( (ClockType::now() - then) >= ms );
       VERIFY( m.locked );
     }
   catch (const std::system_error& e)
@@ -79,8 +80,28 @@ void test01()
     }
 }
 
+/* User defined clock that ticks in two-thousandths of a second
+   forty-two minutes ahead of steady_clock. */
+struct user_defined_clock
+{
+  typedef std::chrono::steady_clock::rep rep;
+  typedef std::ratio<1,2000> period;
+  typedef std::chrono::duration<rep, period> duration;
+  typedef std::chrono::time_point<user_defined_clock> time_point;
+
+  const bool is_steady = true;
+
+  static time_point now() noexcept
+  {
+    using namespace std::chrono;
+    return time_point(duration_cast<duration>(steady_clock::now().time_since_epoch()) + minutes(42));
+  }
+};
+
 int main()
 {
-  test01();
+  test01<std::chrono::steady_clock>();
+  test01<std::chrono::system_clock>();
+  test01<user_defined_clock>();
   return 0;
 }
