There should be no need to check for tzset() as it is POSIX.

config.h.in

@@ -802,9 +802,6 @@
 /* Define to 1 if you have the `ttyslot' function. */
 #undef HAVE_TTYSLOT
 
-/* Define to 1 if you have the `tzset' function. */
-#undef HAVE_TZSET
-
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 

configure

@@ -2655,7 +2655,6 @@ as_fn_append ac_header_list " sys/sysmacros.h"
 as_fn_append ac_func_list " killpg"
 as_fn_append ac_func_list " nl_langinfo"
 as_fn_append ac_func_list " strftime"
-as_fn_append ac_func_list " tzset"
 as_fn_append ac_func_list " seteuid"
 # Check that the precious variables saved in the cache have kept the same
 # value.
@@ -17960,8 +17959,6 @@ done
 
 
 
-
-
 for ac_func in getgrouplist
 do :
   ac_fn_c_check_func "$LINENO" "getgrouplist" "ac_cv_func_getgrouplist"

configure.ac

@@ -2400,7 +2400,7 @@ dnl
 dnl Function checks
 dnl
 AC_FUNC_GETGROUPS
-AC_CHECK_FUNCS_ONCE([killpg nl_langinfo strftime tzset])
+AC_CHECK_FUNCS_ONCE([killpg nl_langinfo strftime])
 AC_CHECK_FUNCS([getgrouplist], [], [
     case "$host_os" in
     aix*)

src/sudo.c

@@ -162,9 +162,7 @@ main(int argc, char *argv[], char *envp[])
     bindtextdomain(PACKAGE_NAME, LOCALEDIR);
     textdomain(PACKAGE_NAME);
 
-#ifdef HAVE_TZSET
     (void) tzset();
-#endif /* HAVE_TZSET */
 
     /* Must be done before we do any password lookups */
 #if defined(HAVE_GETPRPWNAM) && defined(HAVE_SET_AUTH_PARAMETERS)