diff --git a/config/c-library.m4 b/config/c-library.m4
index 6f2b0fbb4e..d9a31d7664 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -26,33 +26,14 @@ fi])# PGAC_VAR_INT_TIMEZONE
 # PGAC_STRUCT_TIMEZONE
 # ------------------
 # Figure out how to get the current timezone.  If `struct tm' has a
-# `tm_zone' member, define `HAVE_TM_ZONE'.  Also, if the
-# external array `tzname' is found, define `HAVE_TZNAME'.
-# This is the same as the standard macro AC_STRUCT_TIMEZONE, except that
-# tzname[] is checked for regardless of whether we find tm_zone.
+# `tm_zone' member, define `HAVE_STRUCT_TM_TM_ZONE'.  Unlike the
+# standard macro AC_STRUCT_TIMEZONE, we don't check for `tzname[]' if
+# not found, since we don't use it.  (We use `int timezone' as a
+# fallback.)
 AC_DEFUN([PGAC_STRUCT_TIMEZONE],
-[AC_REQUIRE([AC_STRUCT_TM])dnl
-AC_CHECK_MEMBERS([struct tm.tm_zone],,,[#include <sys/types.h>
-#include <$ac_cv_struct_tm>
-])
-if test "$ac_cv_member_struct_tm_tm_zone" = yes; then
-  AC_DEFINE(HAVE_TM_ZONE, 1,
-            [Define to 1 if your `struct tm' has `tm_zone'. Deprecated, use
-             `HAVE_STRUCT_TM_TM_ZONE' instead.])
-fi
-AC_CACHE_CHECK(for tzname, ac_cv_var_tzname,
-[AC_LINK_IFELSE([AC_LANG_PROGRAM(
-[[#include <stdlib.h>
+[AC_CHECK_MEMBERS([struct tm.tm_zone],,,[#include <sys/types.h>
 #include <time.h>
-#ifndef tzname /* For SGI.  */
-extern char *tzname[]; /* RS6000 and others reject char **tzname.  */
-#endif
-]],
-[atoi(*tzname);])], ac_cv_var_tzname=yes, ac_cv_var_tzname=no)])
-if test $ac_cv_var_tzname = yes; then
-    AC_DEFINE(HAVE_TZNAME, 1,
-              [Define to 1 if you have the external array `tzname'.])
-fi
+])
 ])# PGAC_STRUCT_TIMEZONE
 
 
diff --git a/configure b/configure
index b3c92764be..74627a7eed 100755
--- a/configure
+++ b/configure
@@ -13964,43 +13964,8 @@ if test x"$pgac_cv_computed_goto" = xyes ; then
 $as_echo "#define HAVE_COMPUTED_GOTO 1" >>confdefs.h
 
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether struct tm is in sys/time.h or time.h" >&5
-$as_echo_n "checking whether struct tm is in sys/time.h or time.h... " >&6; }
-if ${ac_cv_struct_tm+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <sys/types.h>
-#include <time.h>
-
-int
-main ()
-{
-struct tm tm;
-				     int *p = &tm.tm_sec;
-				     return !p;
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_struct_tm=time.h
-else
-  ac_cv_struct_tm=sys/time.h
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_struct_tm" >&5
-$as_echo "$ac_cv_struct_tm" >&6; }
-if test $ac_cv_struct_tm = sys/time.h; then
-
-$as_echo "#define TM_IN_SYS_TIME 1" >>confdefs.h
-
-fi
-
 ac_fn_c_check_member "$LINENO" "struct tm" "tm_zone" "ac_cv_member_struct_tm_tm_zone" "#include <sys/types.h>
-#include <$ac_cv_struct_tm>
+#include <time.h>
 
 "
 if test "x$ac_cv_member_struct_tm_tm_zone" = xyes; then :
@@ -14012,47 +13977,6 @@ _ACEOF
 
 fi
 
-if test "$ac_cv_member_struct_tm_tm_zone" = yes; then
-
-$as_echo "#define HAVE_TM_ZONE 1" >>confdefs.h
-
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for tzname" >&5
-$as_echo_n "checking for tzname... " >&6; }
-if ${ac_cv_var_tzname+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-#include <time.h>
-#ifndef tzname /* For SGI.  */
-extern char *tzname[]; /* RS6000 and others reject char **tzname.  */
-#endif
-
-int
-main ()
-{
-atoi(*tzname);
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_var_tzname=yes
-else
-  ac_cv_var_tzname=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_var_tzname" >&5
-$as_echo "$ac_cv_var_tzname" >&6; }
-if test $ac_cv_var_tzname = yes; then
-
-$as_echo "#define HAVE_TZNAME 1" >>confdefs.h
-
-fi
 
 ac_fn_c_check_type "$LINENO" "union semun" "ac_cv_type_union_semun" "#include <sys/types.h>
 #ifdef HAVE_SYS_IPC_H
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index c6014e83fa..53e6fe3398 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -654,16 +654,9 @@
 /* Define to 1 if you have the <termios.h> header file. */
 #undef HAVE_TERMIOS_H
 
-/* Define to 1 if your `struct tm' has `tm_zone'. Deprecated, use
-   `HAVE_STRUCT_TM_TM_ZONE' instead. */
-#undef HAVE_TM_ZONE
-
 /* Define to 1 if your compiler understands `typeof' or something similar. */
 #undef HAVE_TYPEOF
 
-/* Define to 1 if you have the external array `tzname'. */
-#undef HAVE_TZNAME
-
 /* Define to 1 if you have the <ucred.h> header file. */
 #undef HAVE_UCRED_H
 
@@ -884,9 +877,6 @@
 /* Define to 1 if strerror_r() returns int. */
 #undef STRERROR_R_INT
 
-/* Define to 1 if your <sys/time.h> declares `struct tm'. */
-#undef TM_IN_SYS_TIME
-
 /* Define to 1 to use ARMv8 CRC Extension. */
 #undef USE_ARMV8_CRC32C
 
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index 5bbf476990..a330df9d9d 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -508,16 +508,9 @@
 /* Define to 1 if you have the <termios.h> header file. */
 /* #undef HAVE_TERMIOS_H */
 
-/* Define to 1 if your `struct tm' has `tm_zone'. Deprecated, use
-   `HAVE_STRUCT_TM_TM_ZONE' instead. */
-/* #undef HAVE_TM_ZONE */
-
 /* Define to 1 if your compiler understands `typeof' or something similar. */
 /* #undef HAVE_TYPEOF */
 
-/* Define to 1 if you have the external array `tzname'. */
-/* #undef HAVE_TZNAME */
-
 /* Define to 1 if the system has the type `uint64'. */
 /* #undef HAVE_UINT64 */
 
@@ -686,9 +679,6 @@
 /* Define to 1 if strerror_r() returns int. */
 /* #undef STRERROR_R_INT */
 
-/* Define to 1 if your <sys/time.h> declares `struct tm'. */
-/* #undef TM_IN_SYS_TIME */
-
 /* Define to 1 to build with assertion checks. (--enable-cassert) */
 /* #undef USE_ASSERT_CHECKING */
 
diff --git a/src/pl/plpython/plpython.h b/src/pl/plpython/plpython.h
index 3a1f0d56d7..dc8fcee001 100644
--- a/src/pl/plpython/plpython.h
+++ b/src/pl/plpython/plpython.h
@@ -28,7 +28,6 @@
  */
 #undef _POSIX_C_SOURCE
 #undef _XOPEN_SOURCE
-#undef HAVE_TZNAME
 
 /*
  * Sometimes python carefully scribbles on our *printf macros.