diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 93331fb529a..b39855d3f58 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,16 @@
 2019-12-02  Mike Crowe  <mac@mcrowe.com>
 
+	Fix try_lock_until and try_lock_shared_until on arbitrary clock
+	* include/std/shared_mutex (shared_timed_mutex::try_lock_until)
+	(shared_timed_mutex::try_lock_shared_until): Loop until the absolute
+	timeout time is reached as measured against the appropriate clock.
+	* testsuite/30_threads/shared_timed_mutex/try_lock_until/1.cc: New
+	file. Test try_lock_until and try_lock_shared_until timeouts against
+	various clocks.
+	* testsuite/30_threads/shared_timed_mutex/try_lock_until/1.cc: New
+	file. Test try_lock_until and try_lock_shared_until timeouts against
+	various clocks.
+
 	Add full steady_clock support to shared_timed_mutex
 	* acinclude.m4 (GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK): Define
 	to check for the presence of both pthread_rwlock_clockrdlock and
diff --git a/libstdc++-v3/include/std/shared_mutex b/libstdc++-v3/include/std/shared_mutex
index cfe2ec078e1..f6cf7e75967 100644
--- a/libstdc++-v3/include/std/shared_mutex
+++ b/libstdc++-v3/include/std/shared_mutex
@@ -554,9 +554,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       bool
       try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
       {
+	// The user-supplied clock may not tick at the same rate as
+	// steady_clock, so we must loop in order to guarantee that
+	// the timeout has expired before returning false.
 	typename _Clock::time_point __now = _Clock::now();
-	auto __rtime = __atime - __now;
-	return try_lock_for(__rtime);
+	do {
+	    auto __rtime = __atime - __now;
+	    if (try_lock_for(__rtime))
+	      return true;
+	    __now = _Clock::now();
+	} while (__atime > __now);
+	return false;
       }
 
     // Shared ownership
@@ -631,9 +639,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       try_lock_shared_until(const chrono::time_point<_Clock,
 						     _Duration>& __atime)
       {
+	// The user-supplied clock may not tick at the same rate as
+	// steady_clock, so we must loop in order to guarantee that
+	// the timeout has expired before returning false.
 	typename _Clock::time_point __now = _Clock::now();
-	auto __rtime = __atime - __now;
-	return try_lock_shared_for(__rtime);
+	do {
+	    auto __rtime = __atime - __now;
+	    if (try_lock_shared_for(__rtime))
+	      return true;
+	    __now = _Clock::now();
+	} while (__atime > __now);
+	return false;
       }
 
 #else // ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)