diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index b1fa5b83295..514926c5c05 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -709,22 +709,36 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif
 
     /// nanoseconds
-    typedef duration<_GLIBCXX_CHRONO_INT64_T, nano> 	    nanoseconds;
+    using nanoseconds	= duration<_GLIBCXX_CHRONO_INT64_T, nano>;
 
     /// microseconds
-    typedef duration<_GLIBCXX_CHRONO_INT64_T, micro> 	    microseconds;
+    using microseconds	= duration<_GLIBCXX_CHRONO_INT64_T, micro>;
 
     /// milliseconds
-    typedef duration<_GLIBCXX_CHRONO_INT64_T, milli> 	    milliseconds;
+    using milliseconds	= duration<_GLIBCXX_CHRONO_INT64_T, milli>;
 
     /// seconds
-    typedef duration<_GLIBCXX_CHRONO_INT64_T> 		    seconds;
+    using seconds	= duration<_GLIBCXX_CHRONO_INT64_T>;
 
     /// minutes
-    typedef duration<_GLIBCXX_CHRONO_INT64_T, ratio< 60>>   minutes;
+    using minutes	= duration<_GLIBCXX_CHRONO_INT64_T, ratio< 60>>;
 
     /// hours
-    typedef duration<_GLIBCXX_CHRONO_INT64_T, ratio<3600>>  hours;
+    using hours		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<3600>>;
+
+#if __cplusplus > 201703L
+    /// days
+    using days		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<86400>>;
+
+    /// weeks
+    using weeks		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<604800>>;
+
+    /// years
+    using years		= duration<_GLIBCXX_CHRONO_INT64_T, ratio<31556952>>;
+
+    /// months
+    using months	= duration<_GLIBCXX_CHRONO_INT64_T, ratio<2629746>>;
+#endif // C++20
 
 #undef _GLIBCXX_CHRONO_INT64_T
 
@@ -732,9 +746,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template<typename _Clock, typename _Dur>
       struct time_point
       {
-	typedef _Clock			  			clock;
-	typedef _Dur		  				duration;
-	typedef typename duration::rep	  			rep;
+	static_assert(__is_duration<_Dur>::value,
+	    "duration must be a specialization of std::chrono::duration");
+
+	typedef _Clock						clock;
+	typedef _Dur						duration;
+	typedef typename duration::rep				rep;
 	typedef typename duration::period			period;
 
 	constexpr time_point() : __d(duration::zero())
@@ -790,7 +807,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 				   time_point<_Clock, _ToDur>>::type
       time_point_cast(const time_point<_Clock, _Dur>& __t)
       {
-	typedef time_point<_Clock, _ToDur> 			__time_point;
+	typedef time_point<_Clock, _ToDur>			__time_point;
 	return __time_point(duration_cast<_ToDur>(__t.time_since_epoch()));
       }
 
@@ -837,7 +854,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	typedef duration<_Rep2, _Period2>			__dur2;
 	typedef typename common_type<_Dur1,__dur2>::type	__ct;
-	typedef time_point<_Clock, __ct> 			__time_point;
+	typedef time_point<_Clock, __ct>			__time_point;
 	return __time_point(__lhs.time_since_epoch() + __rhs);
       }
 
@@ -851,7 +868,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	typedef duration<_Rep1, _Period1>			__dur1;
 	typedef typename common_type<__dur1,_Dur2>::type	__ct;
-	typedef time_point<_Clock, __ct> 			__time_point;
+	typedef time_point<_Clock, __ct>			__time_point;
 	return __time_point(__rhs.time_since_epoch() + __lhs);
       }
 
@@ -865,7 +882,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	typedef duration<_Rep2, _Period2>			__dur2;
 	typedef typename common_type<_Dur1,__dur2>::type	__ct;
-	typedef time_point<_Clock, __ct> 			__time_point;
+	typedef time_point<_Clock, __ct>			__time_point;
 	return __time_point(__lhs.time_since_epoch() -__rhs);
       }
 
@@ -946,9 +963,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     */
     struct system_clock
     {
-      typedef chrono::nanoseconds     				duration;
-      typedef duration::rep    					rep;
-      typedef duration::period 					period;
+      typedef chrono::nanoseconds				duration;
+      typedef duration::rep					rep;
+      typedef duration::period					period;
       typedef chrono::time_point<system_clock, duration> 	time_point;
 
       static_assert(system_clock::duration::min()
@@ -986,10 +1003,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     */
     struct steady_clock
     {
-      typedef chrono::nanoseconds 				duration;
-      typedef duration::rep	  				rep;
-      typedef duration::period	  				period;
-      typedef chrono::time_point<steady_clock, duration> 	time_point;
+      typedef chrono::nanoseconds				duration;
+      typedef duration::rep					rep;
+      typedef duration::period					period;
+      typedef chrono::time_point<steady_clock, duration>	time_point;
 
       static constexpr bool is_steady = true;
 
@@ -1014,6 +1031,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template<typename _Duration>
       using sys_time = time_point<system_clock, _Duration>;
     using sys_seconds = sys_time<seconds>;
+    using sys_days = sys_time<days>;
 
     using file_clock = ::std::filesystem::__file_clock;
 
@@ -1027,6 +1045,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template<> inline constexpr bool is_clock_v<system_clock> = true;
     template<> inline constexpr bool is_clock_v<steady_clock> = true;
     template<> inline constexpr bool is_clock_v<file_clock> = true;
+
+    struct local_t { };
+    template<typename _Duration>
+      using local_time = time_point<local_t, _Duration>;
+    using local_seconds = local_time<seconds>;
+    using local_days = local_time<days>;
 #endif // C++20
 
     // @}
diff --git a/libstdc++-v3/testsuite/20_util/time_point/requirements/duration_neg.cc b/libstdc++-v3/testsuite/20_util/time_point/requirements/duration_neg.cc
new file mode 100644
index 00000000000..5e3bc7f1a55
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/time_point/requirements/duration_neg.cc
@@ -0,0 +1,32 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do compile { target c++11 } }
+
+#include <chrono>
+
+namespace chrono = std::chrono;
+
+// A duration-like type
+struct durayshun : chrono::seconds
+{
+  using duration::duration;
+  durayshun(chrono::seconds);
+};
+
+chrono::time_point<chrono::system_clock, durayshun> t; // { dg-error "here" }
+// { dg-error "specialization of std::chrono::duration" "" { target *-*-* } 0 }
diff --git a/libstdc++-v3/testsuite/std/time/clock/file/members.cc b/libstdc++-v3/testsuite/std/time/clock/file/members.cc
new file mode 100644
index 00000000000..44ae717a6ee
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/clock/file/members.cc
@@ -0,0 +1,39 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <chrono>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  auto sys_now = std::chrono::system_clock::now();
+  auto file_now = std::chrono::file_clock::now();
+  auto d1 = std::chrono::file_clock::to_sys(file_now) - sys_now;
+  VERIFY( d1 < std::chrono::seconds(1) );
+  auto d2 = file_now - std::chrono::file_clock::from_sys(sys_now);
+  VERIFY( d2 == d1 );
+}
+
+int
+main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/std/time/clock/file/overview.cc b/libstdc++-v3/testsuite/std/time/clock/file/overview.cc
new file mode 100644
index 00000000000..3ca530dc249
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/clock/file/overview.cc
@@ -0,0 +1,43 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <chrono>
+
+using std::chrono::file_clock;
+
+// Cpp17Clock requirements:
+
+// New type so that is_clock<file_clock> specialization isn't used.
+struct C : file_clock { };
+static_assert( std::chrono::is_clock_v<C> );
+
+// Cpp17TrivialClock requirements:
+
+// A trivial clock's rep must be a numeric type, which is true for
+// libstdc++ because we use an integral type.
+static_assert( std::is_integral_v<file_clock::rep> );
+
+// We meet the recursive Cpp17TrivialClock requirement by using the same clock:
+static_assert( std::is_same_v<file_clock::time_point::clock, file_clock> );
+
+// chrono::file_clock requirements:
+
+static_assert( std::is_signed_v<file_clock::rep> );
+static_assert( noexcept(file_clock::now()) );
diff --git a/libstdc++-v3/testsuite/std/time/syn_c++20.cc b/libstdc++-v3/testsuite/std/time/syn_c++20.cc
new file mode 100644
index 00000000000..5ea7a0f4280
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/syn_c++20.cc
@@ -0,0 +1,199 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <chrono>
+
+#ifndef __cpp_lib_chrono
+# error "Feature test macro for chrono is missing in <chrono>"
+// FIXME
+// #elif __cpp_lib_chrono < 201907L
+// # error "Feature test macro for chrono has wrong value in <chrono>"
+#endif
+
+namespace __gnu_test
+{
+  // Check for the new additions to <chrono> in C++20
+
+  using std::chrono::is_clock;
+  using std::chrono::is_clock_v;
+
+  using std::chrono::days;
+  using std::chrono::weeks;
+  using std::chrono::years;
+  using std::chrono::months;
+
+  using std::chrono::sys_time;
+  using std::chrono::sys_seconds;
+  using std::chrono::sys_days;
+
+  // FIXME
+#if 0
+  using std::chrono::utc_clock;
+  using std::chrono::utc_time;
+  using std::chrono::utc_seconds;
+
+  using std::chrono::leap_second_info;
+  using std::chrono::get_leap_second_info;
+
+  using std::chrono::tai_clock;
+  using std::chrono::tai_time;
+  using std::chrono::tai_seconds;
+
+  using std::chrono::gps_clock;
+  using std::chrono::gps_time;
+  using std::chrono::gps_seconds;
+#endif
+
+  using std::chrono::file_clock;
+  using std::chrono::file_time;
+
+  using std::chrono::local_t;
+  using std::chrono::local_time;
+  using std::chrono::local_seconds;
+  using std::chrono::local_days;
+
+  // FIXME
+#if 0
+  using std::chrono::clock_time_conversion;
+  using std::chrono::clock_cast;
+
+  using std::chrono::last_spec;
+
+  using std::chrono::day;
+  using std::chrono::month;
+  using std::chrono::year;
+  using std::chrono::weekday;
+  using std::chrono::weekday_indexed;
+  using std::chrono::weekday_last;
+  using std::chrono::month_day;
+  using std::chrono::month_day_last;
+  using std::chrono::month_weekday;
+  using std::chrono::month_weekday_last;
+  using std::chrono::year_month;
+  using std::chrono::year_month_day;
+  using std::chrono::year_month_day_last;
+  using std::chrono::year_month_weekday;
+  using std::chrono::year_month_weekday_last;
+  using std::chrono::year_month;
+  using std::chrono::year_month_day;
+
+  using std::chrono::hh_mm_ss;
+  using std::chrono::is_am;
+  using std::chrono::is_pm;
+  using std::chrono::make12;
+  using std::chrono::make24;
+
+  using std::chrono::tzdb;
+  using std::chrono::tzdb_list;
+  using std::chrono::get_tzdb;
+  using std::chrono::get_tzdb_list;
+  using std::chrono::locate_zone;
+  using std::chrono::current_zone;
+
+  using std::chrono::reload_tzdb;
+  using std::chrono::remote_version;
+
+  using std::chrono::nonexistent_local_time;
+  using std::chrono::ambiguous_local_time;
+
+  using std::chrono::sys_info;
+  using std::chrono::local_info;
+
+  using std::chrono::choose;
+  using std::chrono::time_zone;
+
+  using std::chrono::zoned_traits;
+  using std::chrono::zoned_time;
+  using std::chrono::zoned_seconds;
+
+  using std::chrono::leap_second;
+
+  using std::chrono::time_zone_link;
+
+  using std::chrono::local_time_format;
+
+  using std::chrono::parse;
+
+  using std::chrono::last;
+  using std::chrono::Sunday;
+  using std::chrono::Monday;
+  using std::chrono::Tuesday;
+  using std::chrono::Wednesday;
+  using std::chrono::Thursday;
+  using std::chrono::Friday;
+  using std::chrono::Saturday;
+
+  using std::chrono::January;
+  using std::chrono::February;
+  using std::chrono::March;
+  using std::chrono::April;
+  using std::chrono::May;
+  using std::chrono::June;
+  using std::chrono::July;
+  using std::chrono::August;
+  using std::chrono::September;
+  using std::chrono::October;
+  using std::chrono::November;
+  using std::chrono::December;
+
+  using std::chrono_literals::operator""d;
+  using std::chrono_literals::operator""y;
+#endif
+
+  template<typename>
+    constexpr bool is_duration = false;
+  template<typename R, typename P>
+    constexpr bool is_duration<std::chrono::duration<R, P>> = true;
+
+  static_assert( is_duration<days> );
+  static_assert( is_duration<weeks> );
+  static_assert( is_duration<years> );
+  static_assert( is_duration<months> );
+
+  template<typename D, typename P>
+    constexpr bool has_period = std::is_same_v<typename D::period, P>;
+
+  using std::ratio;
+  using std::ratio_multiply;
+  using std::ratio_divide;
+  using std::chrono::hours;
+  static_assert( has_period<days, ratio_multiply<ratio<24>, hours::period>> );
+  static_assert( has_period<weeks, ratio_multiply<ratio<7>, days::period>> );
+  static_assert( has_period<years,
+			    ratio_multiply<ratio<146097, 400>, days::period>> );
+  static_assert( has_period<months, ratio_divide<years::period, ratio<12>>> );
+
+  template<typename>
+    constexpr bool is_time_point = false;
+  template<typename C, typename D>
+    constexpr bool is_time_point<std::chrono::time_point<C, D>> = true;
+
+  static_assert( is_time_point<sys_time<std::chrono::milliseconds>> );
+  static_assert( is_time_point<sys_seconds> );
+  static_assert( is_time_point<sys_days> );
+
+  static_assert( std::is_class_v<local_t> );
+  static_assert( is_time_point<local_time<std::chrono::milliseconds>> );
+  static_assert( is_time_point<local_seconds> );
+  static_assert( is_time_point<local_days> );
+
+  static_assert( std::is_class_v<file_clock> );
+  static_assert( is_time_point<file_time<std::chrono::milliseconds>> );
+}
diff --git a/libstdc++-v3/testsuite/std/time/traits/is_clock.cc b/libstdc++-v3/testsuite/std/time/traits/is_clock.cc
index 85f118253c3..f5d449cd42a 100644
--- a/libstdc++-v3/testsuite/std/time/traits/is_clock.cc
+++ b/libstdc++-v3/testsuite/std/time/traits/is_clock.cc
@@ -35,9 +35,26 @@ static_assert( chrono::is_clock_v<chrono::steady_clock> );
 static_assert(chrono::is_clock<chrono::file_clock>::value);
 static_assert(chrono::is_clock_v<chrono::file_clock>);
 
+// Clock<xxx_clock> will not use the specialization of is_clock<xxx_clock>
+template<typename C> struct Clock : C { };
+
+static_assert( chrono::is_clock<Clock<chrono::system_clock>>::value );
+static_assert( chrono::is_clock_v<Clock<chrono::system_clock>> );
+
+static_assert( chrono::is_clock<Clock<chrono::high_resolution_clock>>::value );
+static_assert( chrono::is_clock_v<Clock<chrono::high_resolution_clock>> );
+
+static_assert( chrono::is_clock<Clock<chrono::steady_clock>>::value );
+static_assert( chrono::is_clock_v<Clock<chrono::steady_clock>> );
+
+static_assert(chrono::is_clock<Clock<chrono::file_clock>>::value);
+static_assert(chrono::is_clock_v<Clock<chrono::file_clock>>);
+
 static_assert( chrono::is_clock<__gnu_test::slow_clock>::value );
 static_assert( chrono::is_clock_v<__gnu_test::slow_clock> );
 
+// Negative tests
+
 static_assert( ! chrono::is_clock<int>::value );
 static_assert( ! chrono::is_clock_v<int> );
 
