Index: libcxx/include/CMakeLists.txt
===================================================================
--- libcxx/include/CMakeLists.txt
+++ libcxx/include/CMakeLists.txt
@@ -162,6 +162,13 @@
   wctype.h
   )
 
+if (ZOS)
+  set(files
+    ${files}
+    support/ibm/nanosleep.h
+    )
+endif()
+
 if(LIBCXX_INSTALL_SUPPORT_HEADERS)
   set(files
     ${files}
Index: libcxx/include/__threading_support
===================================================================
--- libcxx/include/__threading_support
+++ libcxx/include/__threading_support
@@ -15,6 +15,10 @@
 #include <iosfwd>
 #include <errno.h>
 
+#ifdef __MVS__
+#include <support/ibm/nanosleep.h>
+#endif
+
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #pragma GCC system_header
 #endif
Index: libcxx/include/support/ibm/nanosleep.h
===================================================================
--- /dev/null
+++ libcxx/include/support/ibm/nanosleep.h
@@ -0,0 +1,38 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_ZOS_NANOSLEEP
+#define _LIBCPP_ZOS_NANOSLEEP
+
+#include <unistd.h>
+
+int nanosleep(const struct timespec* req, struct timespec* rem)
+{
+   // The nanosleep() function is not available on z/OS. Therefore, we will call
+   // sleep() to sleep for whole seconds and usleep() to sleep for any remaining
+   // fraction of a second. Any remaining nanoseconds will round up to the next
+   // microsecond.
+
+   useconds_t __micro_sec = (rem->tv_nsec + 999) / 1000;
+   if (__micro_sec > 999999)
+   {
+     ++rem->tv_sec;
+     __micro_sec -= 1000000;
+   }
+   while (rem->tv_sec)
+      rem->tv_sec = sleep(rem->tv_sec);
+   if (__micro_sec) {
+     rem->tv_nsec = __micro_sec * 1000;
+     return usleep(__micro_sec);
+   }
+   rem->tv_nsec = 0;
+   return 0;
+}
+
+#endif // _LIBCPP_ZOS_NANOSLEEP
Index: libcxx/src/filesystem/filesystem_common.h
===================================================================
--- libcxx/src/filesystem/filesystem_common.h
+++ libcxx/src/filesystem/filesystem_common.h
@@ -198,6 +198,7 @@
 using chrono::duration_cast;
 
 using TimeSpec = struct ::timespec;
+using TimeVal = struct ::timeval;
 using StatT = struct ::stat;
 
 template <class FileTimeT, class TimeT,
@@ -382,24 +383,36 @@
 #if defined(__APPLE__)
 TimeSpec extract_mtime(StatT const& st) { return st.st_mtimespec; }
 TimeSpec extract_atime(StatT const& st) { return st.st_atimespec; }
+#elif defined(__MVS__)
+TimeSpec extract_mtime(StatT const& st) {
+  TimeSpec TS = {st.st_mtime, 0};
+  return TS;
+}
+TimeSpec extract_atime(StatT const& st) {
+  TimeSpec TS = {st.st_atime, 0};
+  return TS;
+}
 #else
 TimeSpec extract_mtime(StatT const& st) { return st.st_mtim; }
 TimeSpec extract_atime(StatT const& st) { return st.st_atim; }
 #endif
 
-// allow the utimes implementation to compile even it we're not going
-// to use it.
-
-bool posix_utimes(const path& p, std::array<TimeSpec, 2> const& TS,
-                  error_code& ec) {
+TimeVal make_timeval(TimeSpec const& ts) {
   using namespace chrono;
   auto Convert = [](long nsec) {
-    using int_type = decltype(std::declval< ::timeval>().tv_usec);
+    using int_type = decltype(std::declval<TimeVal>().tv_usec);
     auto dur = duration_cast<microseconds>(nanoseconds(nsec)).count();
     return static_cast<int_type>(dur);
   };
-  struct ::timeval ConvertedTS[2] = {{TS[0].tv_sec, Convert(TS[0].tv_nsec)},
-                                     {TS[1].tv_sec, Convert(TS[1].tv_nsec)}};
+  TimeVal TV = {};
+  TV.tv_sec = ts.tv_sec;
+  TV.tv_usec = Convert(ts.tv_nsec);
+  return TV;
+}
+
+bool posix_utimes(const path& p, std::array<TimeSpec, 2> const& TS,
+                  error_code& ec) {
+  TimeVal ConvertedTS[2] = {make_timeval(TS[0]), make_timeval(TS[1])};
   if (::utimes(p.c_str(), ConvertedTS) == -1) {
     ec = capture_errno();
     return true;