diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -183,7 +183,7 @@
 
 #if defined(__apple_build_version__)
 #  define _LIBCPP_COMPILER_CLANG_BASED
-#  define _LIBCPP_APPLE_CLANG_VER (__clang_major__ * 100 + __clang_minor__)
+#  define _LIBCPP_APPLE_CLANG_VER (__apple_build_version__ / 10000)
 #elif defined(__clang__)
 #  define _LIBCPP_COMPILER_CLANG_BASED
 #  define _LIBCPP_CLANG_VER (__clang_major__ * 100 + __clang_minor__)
@@ -509,8 +509,8 @@
 #define _LIBCPP_ALWAYS_INLINE __attribute__ ((__always_inline__))
 
 // Literal operators ""d and ""y are supported starting with LLVM Clang 8 and AppleClang 10.0.1
-#if (defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER < 800) || \
-    (defined(__apple_build_version__) && __apple_build_version__ < 10010000)
+#if (defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER < 800) ||                 \
+    (defined(_LIBCPP_APPLE_CLANG_VER) && _LIBCPP_APPLE_CLANG_VER < 1001)
 #define _LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS
 #endif