diff --git a/include/rp6502.h b/include/rp6502.h
index 33e983de3..c1f60d89a 100644
--- a/include/rp6502.h
+++ b/include/rp6502.h
@@ -129,6 +129,10 @@ int __fastcall__ read_xram (unsigned buf, unsigned count, int fildes);
 int __fastcall__ write_xstack (const void* buf, unsigned count, int fildes);
 int __fastcall__ write_xram (unsigned buf, unsigned count, int fildes);
 
+/* Time zone hack */
+
+void ria_tzset (unsigned long time);
+
 /* XREG location helpers */
 
 #define xreg_ria_keyboard(...) xreg(0, 0, 0, __VA_ARGS__)
diff --git a/include/time.h b/include/time.h
index d320fe3f1..5eb6f144a 100644
--- a/include/time.h
+++ b/include/time.h
@@ -134,7 +134,6 @@ extern struct _timezone {
 int __fastcall__ clock_getres (clockid_t clock_id, struct timespec *res);
 int __fastcall__ clock_gettime (clockid_t clock_id, struct timespec *tp);
 int __fastcall__ clock_settime (clockid_t clock_id, const struct timespec *tp);
-void tzset (void);
 
 #endif
 
diff --git a/libsrc/rp6502/gettimezone.c b/libsrc/rp6502/gettimezone.c
index f3cb2a061..86d0fefcc 100644
--- a/libsrc/rp6502/gettimezone.c
+++ b/libsrc/rp6502/gettimezone.c
@@ -1,10 +1,11 @@
 #include <rp6502.h>
 #include <time.h>
 
-int clock_gettimezone (clockid_t clock_id, struct _timezone* tz)
+int clock_gettimezone (time_t time, clockid_t clock_id, struct _timezone* tz)
 {
     int ax;
     ria_set_ax (clock_id);
+    ria_push_long (time);
     ax = ria_call_int_errno (RIA_OP_CLOCK_GETTIMEZONE);
     if (ax >= 0) {
         char i;
diff --git a/libsrc/rp6502/ria_tzset.c b/libsrc/rp6502/ria_tzset.c
new file mode 100644
index 000000000..3f39e44f2
--- /dev/null
+++ b/libsrc/rp6502/ria_tzset.c
@@ -0,0 +1,9 @@
+#include <rp6502.h>
+#include <time.h>
+
+int clock_gettimezone (time_t time, clockid_t clock_id, struct _timezone* tz);
+
+void ria_tzset (unsigned long time)
+{
+    clock_gettimezone (time, CLOCK_REALTIME, &_tz);
+}
diff --git a/libsrc/rp6502/sysremove.c b/libsrc/rp6502/sysremove.c
index 22d2a65fc..2f1bcadbb 100644
--- a/libsrc/rp6502/sysremove.c
+++ b/libsrc/rp6502/sysremove.c
@@ -7,8 +7,8 @@ unsigned char __fastcall__ _sysremove (const char* name)
     size_t namelen;
     namelen = strlen (name);
     if (namelen > 255) {
-        RIA.errno = EINVAL;
-        return __mappederrno(RIA.errno);
+        RIA.errno_ = EINVAL;
+        return __mappederrno (RIA.errno_);
     }
     while (namelen) {
         ria_push_char (name[--namelen]);
diff --git a/libsrc/rp6502/sysrename.c b/libsrc/rp6502/sysrename.c
index e05ad725a..f61e96a1d 100644
--- a/libsrc/rp6502/sysrename.c
+++ b/libsrc/rp6502/sysrename.c
@@ -8,8 +8,8 @@ unsigned char __fastcall__ _sysrename (const char* oldpath, const char* newpath)
     oldpathlen = strlen (oldpath);
     newpathlen = strlen (newpath);
     if (oldpathlen + newpathlen > 510) {
-        RIA.errno = EINVAL;
-        return __mappederrno(RIA.errno);
+        RIA.errno_ = EINVAL;
+        return __mappederrno (RIA.errno_);
     }
     while (oldpathlen) {
         ria_push_char (oldpath[--oldpathlen]);
diff --git a/libsrc/rp6502/tzset.c b/libsrc/rp6502/tzset.c
deleted file mode 100644
index be4236f2f..000000000
--- a/libsrc/rp6502/tzset.c
+++ /dev/null
@@ -1,9 +0,0 @@
-#include <rp6502.h>
-#include <time.h>
-
-int clock_gettimezone (clockid_t clock_id, struct _timezone* tz);
-
-void tzset (void)
-{
-    clock_gettimezone (CLOCK_REALTIME, &_tz);
-}
diff --git a/libsrc/rp6502/write_xstack.c b/libsrc/rp6502/write_xstack.c
index b356ec706..1df1fd706 100644
--- a/libsrc/rp6502/write_xstack.c
+++ b/libsrc/rp6502/write_xstack.c
@@ -5,8 +5,8 @@ int __fastcall__ write_xstack (const void* buf, unsigned count, int fildes)
 {
     unsigned i;
     if (count > 512) {
-        RIA.errno = EINVAL;
-        return __mappederrno(RIA.errno);
+        RIA.errno_ = EINVAL;
+        return __mappederrno (RIA.errno_);
     }
     for (i = count; i;) {
         ria_push_char (((char*)buf)[--i]);