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
@@ -11,9 +11,7 @@
 #define _LIBCPP___CHRONO_CONVERT_TO_TM_H
 
 #include <__chrono/day.h>
-#include <__concepts/same_as.h>
 #include <__config>
-#include <ctime>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -23,18 +21,14 @@
 
 #if _LIBCPP_STD_VER > 17
 
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI tm __convert_to_tm(const _Tp& __value) {
-  tm __result = {};
+// Convert chrono::days to the given tm type, which must have the same properties as std::tm.
+template <class _Tm>
+_LIBCPP_HIDE_FROM_ABI _Tm __convert_to_tm(const chrono::day& __value) {
+  _Tm __result = {};
 #  ifdef __GLIBC__
   __result.tm_zone = "UTC";
 #  endif
-
-  if constexpr (same_as<_Tp, chrono::day>)
-    __result.tm_mday = static_cast<unsigned>(__value);
-  else
-    static_assert(sizeof(_Tp) == 0, "Add the missing type specialization");
-
+  __result.tm_mday = static_cast<unsigned>(__value);
   return __result;
 }
 
diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
--- a/libcxx/include/__chrono/formatter.h
+++ b/libcxx/include/__chrono/formatter.h
@@ -55,7 +55,7 @@
 template <class _CharT, class _Tp>
 _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
     const _Tp& __value, basic_stringstream<_CharT>& __sstr, basic_string_view<_CharT> __chrono_specs) {
-  tm __t              = std::__convert_to_tm(__value);
+  tm __t              = std::__convert_to_tm<tm>(__value);
   const auto& __facet = std::use_facet<time_put<_CharT>>(__sstr.getloc());
   for (auto __it = __chrono_specs.begin(); __it != __chrono_specs.end(); ++__it) {
     if (*__it == _CharT('%')) {
diff --git a/libcxx/test/std/time/time.cal/time.cal.day/time.cal.day.nonmembers/ostream.pass.cpp b/libcxx/test/std/time/time.cal/time.cal.day/time.cal.day.nonmembers/ostream.pass.cpp
--- a/libcxx/test/std/time/time.cal/time.cal.day/time.cal.day.nonmembers/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.cal/time.cal.day/time.cal.day.nonmembers/ostream.pass.cpp
@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: libcpp-has-no-localization
+// UNSUPPORTED: no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
 // TODO FMT Investigate Windows issues.
diff --git a/libcxx/test/std/time/time.syn/formatter.day.pass.cpp b/libcxx/test/std/time/time.syn/formatter.day.pass.cpp
--- a/libcxx/test/std/time/time.syn/formatter.day.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.day.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
-// UNSUPPORTED: libcpp-has-no-localization
+// UNSUPPORTED: no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
 // TODO FMT Investigate Windows issues.