diff --git a/libcxx/include/__chrono/convert_to_tm.h b/libcxx/include/__chrono/convert_to_tm.h
--- a/libcxx/include/__chrono/convert_to_tm.h
+++ b/libcxx/include/__chrono/convert_to_tm.h
@@ -78,7 +78,7 @@
 
 template <class _Tm, class _Duration>
 _LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const chrono::sys_time<_Duration> __tp) {
-  chrono::sys_days __days = chrono::time_point_cast<chrono::days>(__tp);
+  chrono::sys_days __days = chrono::floor<chrono::days>(__tp);
   chrono::year_month_day __ymd{__days};
 
   _Tm __result = std::__convert_to_tm<_Tm>(chrono::year_month_day{__ymd}, chrono::weekday{__days});
diff --git a/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp
--- a/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.file_time.pass.cpp
@@ -49,10 +49,30 @@
   std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
 
   // Non localized output
+
+  // [time.syn]
+  //   using nanoseconds  = duration<signed integer type of at least 64 bits, nano>;
+  //   using microseconds = duration<signed integer type of at least 55 bits, micro>;
+  //   using milliseconds = duration<signed integer type of at least 45 bits, milli>;
+  //   using seconds      = duration<signed integer type of at least 35 bits>;
+  //   using minutes      = duration<signed integer type of at least 29 bits, ratio<  60>>;
+  //   using hours        = duration<signed integer type of at least 23 bits, ratio<3600>>;
+  check(SV("1425-08-04 22:06:56"), SV("{}"), file_seconds(-17'179'869'184s)); // Minimum value for 35 bits.
+  check(SV("1901-12-13 20:45:52"), SV("{}"), file_seconds(-2'147'483'648s));
+
+  check(SV("1969-12-31 00:00:00"), SV("{}"), file_seconds(-24h));
+  check(SV("1969-12-31 06:00:00"), SV("{}"), file_seconds(-18h));
+  check(SV("1969-12-31 12:00:00"), SV("{}"), file_seconds(-12h));
+  check(SV("1969-12-31 18:00:00"), SV("{}"), file_seconds(-6h));
+  check(SV("1969-12-31 23:59:59"), SV("{}"), file_seconds(-1s));
+
   check(SV("1970-01-01 00:00:00"), SV("{}"), file_seconds(0s));
   check(SV("2000-01-01 00:00:00"), SV("{}"), file_seconds(946'684'800s));
   check(SV("2000-01-01 01:02:03"), SV("{}"), file_seconds(946'688'523s));
 
+  check(SV("2038-01-19 03:14:07"), SV("{}"), file_seconds(2'147'483'647s));
+  check(SV("2514-05-30 01:53:03"), SV("{}"), file_seconds(17'179'869'183s)); // Maximum value for 35 bits.
+
   check(SV("2000-01-01 01:02:03.123"), SV("{}"), file_time<std::chrono::milliseconds>(946'688'523'123ms));
 
   std::locale::global(std::locale::classic());
diff --git a/libcxx/test/std/time/time.syn/formatter.local_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.local_time.pass.cpp
--- a/libcxx/test/std/time/time.syn/formatter.local_time.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.local_time.pass.cpp
@@ -42,10 +42,31 @@
   std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
 
   // Non localized output
+
+  // [time.syn]
+  //   using nanoseconds  = duration<signed integer type of at least 64 bits, nano>;
+  //   using microseconds = duration<signed integer type of at least 55 bits, micro>;
+  //   using milliseconds = duration<signed integer type of at least 45 bits, milli>;
+  //   using seconds      = duration<signed integer type of at least 35 bits>;
+  //   using minutes      = duration<signed integer type of at least 29 bits, ratio<  60>>;
+  //   using hours        = duration<signed integer type of at least 23 bits, ratio<3600>>;
+  check(
+      SV("1425-08-04 22:06:56"), SV("{}"), std::chrono::local_seconds(-17'179'869'184s)); // Minimum value for 35 bits.
+  check(SV("1901-12-13 20:45:52"), SV("{}"), std::chrono::local_seconds(-2'147'483'648s));
+
+  check(SV("1969-12-31 00:00:00"), SV("{}"), std::chrono::local_seconds(-24h));
+  check(SV("1969-12-31 06:00:00"), SV("{}"), std::chrono::local_seconds(-18h));
+  check(SV("1969-12-31 12:00:00"), SV("{}"), std::chrono::local_seconds(-12h));
+  check(SV("1969-12-31 18:00:00"), SV("{}"), std::chrono::local_seconds(-6h));
+  check(SV("1969-12-31 23:59:59"), SV("{}"), std::chrono::local_seconds(-1s));
+
   check(SV("1970-01-01 00:00:00"), SV("{}"), std::chrono::local_seconds(0s));
   check(SV("2000-01-01 00:00:00"), SV("{}"), std::chrono::local_seconds(946'684'800s));
   check(SV("2000-01-01 01:02:03"), SV("{}"), std::chrono::local_seconds(946'688'523s));
 
+  check(SV("2038-01-19 03:14:07"), SV("{}"), std::chrono::local_seconds(2'147'483'647s));
+  check(SV("2514-05-30 01:53:03"), SV("{}"), std::chrono::local_seconds(17'179'869'183s)); // Maximum value for 35 bits.
+
   check(SV("2000-01-01 01:02:03.123"), SV("{}"), std::chrono::local_time<std::chrono::milliseconds>(946'688'523'123ms));
 
   std::locale::global(std::locale::classic());
diff --git a/libcxx/test/std/time/time.syn/formatter.sys_time.pass.cpp b/libcxx/test/std/time/time.syn/formatter.sys_time.pass.cpp
--- a/libcxx/test/std/time/time.syn/formatter.sys_time.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.sys_time.pass.cpp
@@ -42,10 +42,30 @@
   std::locale::global(std::locale(LOCALE_fr_FR_UTF_8));
 
   // Non localized output
+
+  // [time.syn]
+  //   using nanoseconds  = duration<signed integer type of at least 64 bits, nano>;
+  //   using microseconds = duration<signed integer type of at least 55 bits, micro>;
+  //   using milliseconds = duration<signed integer type of at least 45 bits, milli>;
+  //   using seconds      = duration<signed integer type of at least 35 bits>;
+  //   using minutes      = duration<signed integer type of at least 29 bits, ratio<  60>>;
+  //   using hours        = duration<signed integer type of at least 23 bits, ratio<3600>>;
+  check(SV("1425-08-04 22:06:56"), SV("{}"), std::chrono::sys_seconds(-17'179'869'184s)); // Minimum value for 35 bits.
+  check(SV("1901-12-13 20:45:52"), SV("{}"), std::chrono::sys_seconds(-2'147'483'648s));
+
+  check(SV("1969-12-31 00:00:00"), SV("{}"), std::chrono::sys_seconds(-24h));
+  check(SV("1969-12-31 06:00:00"), SV("{}"), std::chrono::sys_seconds(-18h));
+  check(SV("1969-12-31 12:00:00"), SV("{}"), std::chrono::sys_seconds(-12h));
+  check(SV("1969-12-31 18:00:00"), SV("{}"), std::chrono::sys_seconds(-6h));
+  check(SV("1969-12-31 23:59:59"), SV("{}"), std::chrono::sys_seconds(-1s));
+
   check(SV("1970-01-01 00:00:00"), SV("{}"), std::chrono::sys_seconds(0s));
   check(SV("2000-01-01 00:00:00"), SV("{}"), std::chrono::sys_seconds(946'684'800s));
   check(SV("2000-01-01 01:02:03"), SV("{}"), std::chrono::sys_seconds(946'688'523s));
 
+  check(SV("2038-01-19 03:14:07"), SV("{}"), std::chrono::sys_seconds(2'147'483'647s));
+  check(SV("2514-05-30 01:53:03"), SV("{}"), std::chrono::sys_seconds(17'179'869'183s)); // Maximum value for 35 bits.
+
   check(SV("2000-01-01 01:02:03.123"), SV("{}"), std::chrono::sys_time<std::chrono::milliseconds>(946'688'523'123ms));
 
   std::locale::global(std::locale::classic());