diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index 4e53cd4aa2e..87caa30b83a 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -2134,7 +2134,7 @@ namespace chrono
       // either "{:L}[{}]" or "{:L}[{} is not a valid index]". The {:L} spec
       // means to format the weekday using ostringstream, so just do that.
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __wdi.weekday();
       const auto __i = __wdi.index();
       if constexpr (is_same_v<_CharT, char>)
@@ -2157,7 +2157,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{:L}[last]"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __wdl.weekday() << _GLIBCXX_WIDEN("[last]");
       __os << __os2.view();
       return __os;
@@ -2169,7 +2169,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{:L}/{}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __md.month();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << '/';
@@ -2189,7 +2189,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{:L}/last"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __mdl.month();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << "/last";
@@ -2206,7 +2206,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{:L}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __mwd.month();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << '/';
@@ -2224,7 +2224,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{:L}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __mwdl.month();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << '/';
@@ -2241,7 +2241,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __ym.year();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << '/';
@@ -2277,7 +2277,7 @@ namespace chrono
     {
       // As above, just write straight to a stringstream, as if by "{}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       __os2 << __ymdl.year();
       if constexpr (is_same_v<_CharT, char>)
 	__os2 << '/';
@@ -2296,7 +2296,7 @@ namespace chrono
       // As above, just write straight to a stringstream, as if by
       // "{}/{:L}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       _CharT __slash;
       if constexpr (is_same_v<_CharT, char>)
 	__slash = '/';
@@ -2316,7 +2316,7 @@ namespace chrono
       // As above, just write straight to a stringstream, as if by
       // "{}/{:L}/{:L}"
       basic_stringstream<_CharT> __os2;
-      __os2.imbue(__os.getloc);
+      __os2.imbue(__os.getloc());
       _CharT __slash;
       if constexpr (is_same_v<_CharT, char>)
 	__slash = '/';
diff --git a/libstdc++-v3/testsuite/std/time/month_day/io.cc b/libstdc++-v3/testsuite/std/time/month_day/io.cc
new file mode 100644
index 00000000000..454231dd724
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/month_day/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << January/14 << ' ' << February/30 << ' ' << March/34;
+  VERIFY( ss.str() == "Jan/14 Feb/30 Mar/34 is not a valid day" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << July/27;
+  VERIFY( ss.str() == "juil./27" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/month_day_last/io.cc b/libstdc++-v3/testsuite/std/time/month_day_last/io.cc
new file mode 100644
index 00000000000..6bd95d9d524
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/month_day_last/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << January/last << ' ' << February/last << ' ' << March/last;
+  VERIFY( ss.str() == "Jan/last Feb/last Mar/last" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << July/last;
+  VERIFY( ss.str() == "juil./last" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/month_weekday/io.cc b/libstdc++-v3/testsuite/std/time/month_weekday/io.cc
new file mode 100644
index 00000000000..a62f84a16aa
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/month_weekday/io.cc
@@ -0,0 +1,31 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << January/Saturday[2] << ' ' << February/Monday[5] << ' '
+    << March/Sunday[8];
+  VERIFY( ss.str() == "Jan/Sat[2] Feb/Mon[5] Mar/Sun[8 is not a valid index]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << July/Thursday[4];
+  VERIFY( ss.str() == "juil./jeu.[4]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/month_weekday_last/io.cc b/libstdc++-v3/testsuite/std/time/month_weekday_last/io.cc
new file mode 100644
index 00000000000..f69cc187ce8
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/month_weekday_last/io.cc
@@ -0,0 +1,31 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << January/Saturday[last] << ' ' << February/Monday[last] << ' '
+    << March/weekday(9)[last];
+  VERIFY( ss.str() == "Jan/Sat[last] Feb/Mon[last] Mar/9 is not a valid weekday[last]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << July/Thursday[last];
+  VERIFY( ss.str() == "juil./jeu.[last]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/weekday_indexed/io.cc b/libstdc++-v3/testsuite/std/time/weekday_indexed/io.cc
new file mode 100644
index 00000000000..cdb91f4ba11
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/weekday_indexed/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << Monday[2] << ' ' << Wednesday[5] << ' ' << Friday[13];
+  VERIFY( ss.str() == "Mon[2] Wed[5] Fri[13 is not a valid index]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << Saturday[1];
+  VERIFY( ss.str() == "sam.[1]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/weekday_last/io.cc b/libstdc++-v3/testsuite/std/time/weekday_last/io.cc
new file mode 100644
index 00000000000..b81830f8f68
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/weekday_last/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << Monday[last] << ' ' << Wednesday[last] << ' ' << weekday(9)[last];
+  VERIFY( ss.str() == "Mon[last] Wed[last] 9 is not a valid weekday[last]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << Saturday[last];
+  VERIFY( ss.str() == "sam.[last]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/year_month/io.cc b/libstdc++-v3/testsuite/std/time/year_month/io.cc
new file mode 100644
index 00000000000..8c0eb9b6579
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/year_month/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << 2023y/January << ' ' << 2023y/month(13);
+  VERIFY( ss.str() == "2023/Jan 2023/13 is not a valid month" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << 2023y/July;
+  VERIFY( ss.str() == "2023/juil." );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/year_month_day_last/io.cc b/libstdc++-v3/testsuite/std/time/year_month_day_last/io.cc
new file mode 100644
index 00000000000..cb60f078c7e
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/year_month_day_last/io.cc
@@ -0,0 +1,30 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << 2023y/January/last << ' ' << 2023y/month(13)/last;
+  VERIFY( ss.str() == "2023/Jan/last 2023/13 is not a valid month/last" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << 2023y/July/last;
+  VERIFY( ss.str() == "2023/juil./last" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/year_month_weekday/io.cc b/libstdc++-v3/testsuite/std/time/year_month_weekday/io.cc
new file mode 100644
index 00000000000..530429ff129
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/year_month_weekday/io.cc
@@ -0,0 +1,42 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << 2023y/January/Saturday[2];
+  VERIFY( ss.str() == "2023/Jan/Sat[2]" );
+  ss.clear();
+  ss.str("");
+  ss << 2023y/month(13)/Monday[1];
+  VERIFY( ss.str() == "2023/13 is not a valid month/Mon[1]" );
+  ss.clear();
+  ss.str("");
+  ss << 2023y/December/weekday(9)[5];
+  VERIFY( ss.str() == "2023/Dec/9 is not a valid weekday[5]" );
+  ss.clear();
+  ss.str("");
+  ss << 2023y/December/Monday[6];
+  VERIFY( ss.str() == "2023/Dec/Mon[6 is not a valid index]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << 2023y/July/Thursday[2];
+  VERIFY( ss.str() == "2023/juil./jeu.[2]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
diff --git a/libstdc++-v3/testsuite/std/time/year_month_weekday_last/io.cc b/libstdc++-v3/testsuite/std/time/year_month_weekday_last/io.cc
new file mode 100644
index 00000000000..f6aff52f7eb
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/year_month_weekday_last/io.cc
@@ -0,0 +1,38 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+// { dg-require-namedlocale "fr_FR.ISO8859-15" }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+void
+test_ostream()
+{
+  using std::ostringstream;
+  using namespace std::chrono;
+
+  ostringstream ss;
+  ss << 2023y/January/Monday[last];
+  VERIFY( ss.str() == "2023/Jan/Mon[last]" );
+  ss.clear();
+  ss.str("");
+  ss << 2023y/month(13)/Monday[last];
+  VERIFY( ss.str() == "2023/13 is not a valid month/Mon[last]" );
+  ss.clear();
+  ss.str("");
+  ss << 2023y/December/weekday(9)[last];
+  VERIFY( ss.str() == "2023/Dec/9 is not a valid weekday[last]" );
+
+  ss.str("");
+  ss.imbue(std::locale(ISO_8859(15,fr_FR)));
+  ss << 2023y/July/Thursday[last];
+  VERIFY( ss.str() == "2023/juil./jeu.[last]" );
+}
+
+int main()
+{
+  test_ostream();
+  // TODO: test_format();
+  // TODO: test_parse();
+}
