diff --git a/hawk/lib/hawk-cmn.h b/hawk/lib/hawk-cmn.h
index 15e041e3..3c50d05a 100644
--- a/hawk/lib/hawk-cmn.h
+++ b/hawk/lib/hawk-cmn.h
@@ -647,11 +647,14 @@ struct hawk_link_t
 #define HAWK_SEC_TO_USEC(sec) ((sec) * HAWK_USECS_PER_SEC)
 #define HAWK_USEC_TO_SEC(usec) ((usec) / HAWK_USECS_PER_SEC)
 
+typedef hawk_int64_t hawk_ntime_sec_t;
+typedef hawk_int32_t hawk_ntime_nsec_t;
+
 typedef struct hawk_ntime_t hawk_ntime_t;
 struct hawk_ntime_t
 {
-	hawk_intptr_t  sec;
-	hawk_int32_t   nsec; /* nanoseconds */
+	hawk_ntime_sec_t  sec;
+	hawk_ntime_nsec_t nsec; /* nanoseconds */
 };
 
 #define HAWK_INIT_NTIME(c,s,ns) (((c)->sec = (s)), ((c)->nsec = (ns)))
diff --git a/hawk/lib/hawk-utl.h b/hawk/lib/hawk-utl.h
index eaeebfb1..9201b28c 100644
--- a/hawk/lib/hawk-utl.h
+++ b/hawk/lib/hawk-utl.h
@@ -1607,24 +1607,31 @@ HAWK_EXPORT int hawk_qsortx (
 /* =========================================================================
  * TIME 
  * ========================================================================= */
-HAWK_EXPORT int hawk_get_time (
+HAWK_EXPORT int hawk_get_ntime (
 	hawk_ntime_t* t
 );
 
-HAWK_EXPORT int hawk_set_time (
+HAWK_EXPORT int hawk_set_ntime (
 	const hawk_ntime_t* t
 );
 
-HAWK_EXPORT void hawk_add_time (
+/**
+ * The hawk_add_ntime() adds two time structures pointed to by x and y and 
+ * stores the result in z. Upon overflow, it sets z to the largest value
+ * the hawk_ntime_t type can represent. Upon underflow, it sets z to the 
+ * smallest value. If you don't need this extra range check, you may use 
+ * the HAWK_ADD_NTIME() macro.
+ */
+HAWK_EXPORT void hawk_add_ntime (
+	hawk_ntime_t*       z,
 	const hawk_ntime_t* x,
-	const hawk_ntime_t* y,
-	hawk_ntime_t*       z
+	const hawk_ntime_t* y
 );
 
-HAWK_EXPORT void hawk_sub_time (
+HAWK_EXPORT void hawk_sub_ntime (
+	hawk_ntime_t*       z,
 	const hawk_ntime_t* x,
-	const hawk_ntime_t* y,
-	hawk_ntime_t*       z
+	const hawk_ntime_t* y
 );
 
 
diff --git a/hawk/lib/mod-math.c b/hawk/lib/mod-math.c
index b0b576bc..8cb9cd8d 100644
--- a/hawk/lib/mod-math.c
+++ b/hawk/lib/mod-math.c
@@ -572,7 +572,7 @@ static int fnc_srand (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 	if (nargs <= 0)
 	{
 		hawk_ntime_t tv;
-		hawk_get_time (&tv);
+		hawk_get_ntime (&tv);
 		modctx->seed = tv.sec + tv.nsec;
 	#if defined(HAVE_INITSTATE_R) && defined(HAVE_SRANDOM_R) && defined(HAVE_RANDOM_R)
 		srandom_r (modctx->seed, &modctx->prand);
@@ -710,7 +710,7 @@ int hawk_mod_math (hawk_mod_t* mod, hawk_t* hawk)
 
 	HAWK_MEMSET (modctx, 0, HAWK_SIZEOF(*modctx));
 
-	hawk_get_time (&tv);
+	hawk_get_ntime (&tv);
 	modctx->seed = tv.sec + tv.nsec;
 #if defined(HAVE_INITSTATE_R) && defined(HAVE_SRANDOM_R) && defined(HAVE_RANDOM_R)
 	initstate_r (0, modctx->prand_bin, HAWK_SIZEOF(modctx->prand_bin), &modctx->prand);
diff --git a/hawk/lib/mod-sys.c b/hawk/lib/mod-sys.c
index a2dff070..1e0ba9d6 100644
--- a/hawk/lib/mod-sys.c
+++ b/hawk/lib/mod-sys.c
@@ -2329,7 +2329,7 @@ static int fnc_gettime (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 	hawk_val_t* retv;
 	hawk_ntime_t now;
 
-	if (hawk_get_time(&now) <= -1) now.sec = 0;
+	if (hawk_get_ntime(&now) <= -1) now.sec = 0;
 
 	retv = hawk_rtx_makeintval(rtx, now.sec);
 	if (!retv) return -1;
@@ -2351,7 +2351,7 @@ static int fnc_settime (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 	else
 	{
 		now.sec = tmp;
-		if (hawk_set_time(&now) <= -1) rx = -1;
+		if (hawk_set_ntime(&now) <= -1) rx = -1;
 		else rx = 0;
 	}
 
@@ -2440,7 +2440,7 @@ static int fnc_mktime (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 	else
 	{
 		/* get the current time when no argument is given */
-		hawk_get_time (&nt);
+		hawk_get_ntime (&nt);
 	}
 
 	retv = hawk_rtx_makeintval(rtx, nt.sec);
@@ -4677,7 +4677,7 @@ static int fnc_writelog (hawk_rtx_t* rtx, const hawk_fnc_info_t* fi)
 				if (!mctx->log.dmsgbuf) goto fail;
 			}
 
-			if (hawk_get_time(&now) <= -1)
+			if (hawk_get_ntime(&now) <= -1)
 			{
 				rx = set_error_on_sys_list(rtx, sys_list, HAWK_ESYSERR, HAWK_T("unable to get time"));
 				goto done;
diff --git a/hawk/lib/mtx.c b/hawk/lib/mtx.c
index c133aea8..c0d41d96 100644
--- a/hawk/lib/mtx.c
+++ b/hawk/lib/mtx.c
@@ -233,8 +233,8 @@ int hawk_mtx_lock (hawk_mtx_t* mtx, const hawk_ntime_t* waiting_time)
 		struct timespec ts;
 		int n;
 
-		hawk_get_time (&t);
-		hawk_add_time (&t, waiting_time, &t);
+		hawk_get_ntime (&t);
+		hawk_add_ntime (&t, waiting_time, &t);
 
 		ts.tv_sec = t.sec;
 		ts.tv_nsec = t.nsec;
@@ -326,7 +326,7 @@ int hawk_mtx_trylock (hawk_mtx_t* mtx)
 	#elif defined(HAVE_PTHREAD_MUTEX_TIMEDLOCK)
 	hawk_ntime_t t;
 	struct timespec ts;
-	hawk_get_time (&t);
+	hawk_get_ntime (&t);
 	ts.tv_sec = t.sec;
 	ts.tv_nsec = t.nsec;
 	n = pthread_mutex_timedlock((pthread_mutex_t*)&mtx->hnd, &ts);
diff --git a/hawk/lib/utl-sys.c b/hawk/lib/utl-sys.c
index 1adb14c6..4ced2c3e 100644
--- a/hawk/lib/utl-sys.c
+++ b/hawk/lib/utl-sys.c
@@ -50,7 +50,7 @@
 #	endif
 #endif
 
-int hawk_get_time (hawk_ntime_t* t)
+int hawk_get_ntime (hawk_ntime_t* t)
 {
 #if defined(_WIN32)
 	SYSTEMTIME st;
@@ -161,7 +161,7 @@ int hawk_get_time (hawk_ntime_t* t)
 #endif
 }
 
-int hawk_set_time (const hawk_ntime_t* t)
+int hawk_set_ntime (const hawk_ntime_t* t)
 {
 #if defined(_WIN32)
 	FILETIME ft;
@@ -243,6 +243,7 @@ int hawk_set_time (const hawk_ntime_t* t)
 #endif
 }
 
+#if 0
 void hawk_add_time (const hawk_ntime_t* x, const hawk_ntime_t* y, hawk_ntime_t* z)
 {
 	/*HAWK_ASSERT (x->nsec >= 0 && x->nsec < HAWK_NSECS_PER_SEC);
@@ -272,4 +273,112 @@ void hawk_sub_time (const hawk_ntime_t* x, const hawk_ntime_t* y, hawk_ntime_t*
 		z->nsec = z->nsec + HAWK_NSECS_PER_SEC;
 	}
 }
+#endif
 
+void hawk_add_ntime (hawk_ntime_t* z, const hawk_ntime_t* x, const hawk_ntime_t* y)
+{
+	hawk_ntime_sec_t xs, ys;
+	hawk_ntime_nsec_t ns;
+
+	HAWK_ASSERT (x->nsec >= 0 && x->nsec < HAWK_NSECS_PER_SEC);
+	HAWK_ASSERT (y->nsec >= 0 && y->nsec < HAWK_NSECS_PER_SEC);
+
+	ns = x->nsec + y->nsec;
+	if (ns >= HAWK_NSECS_PER_SEC)
+	{
+		ns = ns - HAWK_NSECS_PER_SEC;
+		if (x->sec == HAWK_TYPE_MAX(hawk_ntime_sec_t))
+		{
+			if (y->sec >= 0) goto overflow;
+			xs = x->sec;
+			ys = y->sec + 1; /* this won't overflow */
+		}
+		else
+		{
+			xs = x->sec + 1; /* this won't overflow */
+			ys = y->sec;
+		}
+	}
+	else
+	{
+		xs = x->sec;
+		ys = y->sec;
+	}
+
+	if ((ys >= 1 && xs > HAWK_TYPE_MAX(hawk_ntime_sec_t) - ys) ||
+	    (ys <= -1 && xs < HAWK_TYPE_MIN(hawk_ntime_sec_t) - ys))
+	{
+		if (xs >= 0)
+		{
+		overflow:
+			xs = HAWK_TYPE_MAX(hawk_ntime_sec_t);
+			ns = HAWK_NSECS_PER_SEC - 1;
+		}
+		else
+		{
+			xs = HAWK_TYPE_MIN(hawk_ntime_sec_t);
+			ns = 0;
+		}
+	}
+	else
+	{
+		xs = xs + ys;
+	}
+
+	z->sec = xs;
+	z->nsec = ns;
+}
+
+void hawk_sub_ntime (hawk_ntime_t* z, const hawk_ntime_t* x, const hawk_ntime_t* y)
+{
+	hawk_ntime_sec_t xs, ys;
+	hawk_ntime_nsec_t ns;
+
+	HAWK_ASSERT (x->nsec >= 0 && x->nsec < HAWK_NSECS_PER_SEC);
+	HAWK_ASSERT (y->nsec >= 0 && y->nsec < HAWK_NSECS_PER_SEC);
+
+	ns = x->nsec - y->nsec;
+	if (ns < 0)
+	{
+		ns = ns + HAWK_NSECS_PER_SEC;
+		if (x->sec == HAWK_TYPE_MIN(hawk_ntime_sec_t))
+		{
+			if (y->sec <= 0) goto underflow;
+			xs = x->sec;
+			ys = y->sec - 1; /* this won't underflow */
+		}
+		else
+		{
+			xs = x->sec - 1; /* this won't underflow */
+			ys = y->sec;
+		}
+	}
+	else
+	{
+		xs = x->sec;
+		ys = y->sec;
+	}
+
+	if ((ys >= 1 && xs < HAWK_TYPE_MIN(hawk_ntime_sec_t) + ys) ||
+	    (ys <= -1 && xs > HAWK_TYPE_MAX(hawk_ntime_sec_t) + ys))
+	{
+		if (xs >= 0)
+		{
+			xs = HAWK_TYPE_MAX(hawk_ntime_sec_t);
+			ns = HAWK_NSECS_PER_SEC - 1;
+		}
+		else
+		{
+		underflow:
+			xs = HAWK_TYPE_MIN(hawk_ntime_sec_t);
+			ns = 0;
+		}
+	} 
+	else
+	{
+		xs = xs - ys;
+	}
+
+	z->sec = xs;
+	z->nsec = ns;
+}
diff --git a/hawk/t/Makefile.am b/hawk/t/Makefile.am
index 03b8f771..945b9008 100644
--- a/hawk/t/Makefile.am
+++ b/hawk/t/Makefile.am
@@ -16,7 +16,7 @@ check_SCRIPTS = h-001.hawk
 ##noinst_SCRIPTS = $(check_SCRIPTS)
 EXTRA_DIST = $(check_SCRIPTS)
 
-check_PROGRAMS = t-001 t-002 t-003 t-004 t-005
+check_PROGRAMS = t-001 t-002 t-003 t-004 t-005 t-006
 
 t_001_SOURCES = t-001.c t.h
 
@@ -36,6 +36,10 @@ t_005_SOURCES = t-005.c t.h
 t_005_LDADD = -lhawk $(LDADD)
 t_005_DEPENDENCIES = ../lib/libhawk.la
 
+t_006_SOURCES = t-006.c t.h
+t_006_LDADD = -lhawk $(LDADD)
+t_006_DEPENDENCIES = ../lib/libhawk.la
+
 
 TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 
diff --git a/hawk/t/Makefile.in b/hawk/t/Makefile.in
index 26297b36..ca95a7aa 100644
--- a/hawk/t/Makefile.in
+++ b/hawk/t/Makefile.in
@@ -88,7 +88,7 @@ POST_UNINSTALL = :
 build_triplet = @build@
 host_triplet = @host@
 check_PROGRAMS = t-001$(EXEEXT) t-002$(EXEEXT) t-003$(EXEEXT) \
-	t-004$(EXEEXT) t-005$(EXEEXT)
+	t-004$(EXEEXT) t-005$(EXEEXT) t-006$(EXEEXT)
 subdir = t
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/m4/ax_check_sign.m4 \
@@ -125,6 +125,8 @@ am_t_004_OBJECTS = t-004.$(OBJEXT)
 t_004_OBJECTS = $(am_t_004_OBJECTS)
 am_t_005_OBJECTS = t-005.$(OBJEXT)
 t_005_OBJECTS = $(am_t_005_OBJECTS)
+am_t_006_OBJECTS = t-006.$(OBJEXT)
+t_006_OBJECTS = $(am_t_006_OBJECTS)
 AM_V_P = $(am__v_P_@AM_V@)
 am__v_P_ = $(am__v_P_@AM_DEFAULT_V@)
 am__v_P_0 = false
@@ -141,7 +143,8 @@ DEFAULT_INCLUDES =
 depcomp = $(SHELL) $(top_srcdir)/ac/depcomp
 am__maybe_remake_depfiles = depfiles
 am__depfiles_remade = ./$(DEPDIR)/t-001.Po ./$(DEPDIR)/t-002.Po \
-	./$(DEPDIR)/t-003.Po ./$(DEPDIR)/t-004.Po ./$(DEPDIR)/t-005.Po
+	./$(DEPDIR)/t-003.Po ./$(DEPDIR)/t-004.Po ./$(DEPDIR)/t-005.Po \
+	./$(DEPDIR)/t-006.Po
 am__mv = mv -f
 COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
 	$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
@@ -162,9 +165,9 @@ am__v_CCLD_ = $(am__v_CCLD_@AM_DEFAULT_V@)
 am__v_CCLD_0 = @echo "  CCLD    " $@;
 am__v_CCLD_1 = 
 SOURCES = $(t_001_SOURCES) $(t_002_SOURCES) $(t_003_SOURCES) \
-	$(t_004_SOURCES) $(t_005_SOURCES)
+	$(t_004_SOURCES) $(t_005_SOURCES) $(t_006_SOURCES)
 DIST_SOURCES = $(t_001_SOURCES) $(t_002_SOURCES) $(t_003_SOURCES) \
-	$(t_004_SOURCES) $(t_005_SOURCES)
+	$(t_004_SOURCES) $(t_005_SOURCES) $(t_006_SOURCES)
 am__can_run_installinfo = \
   case $$AM_UPDATE_INFO_DIR in \
     n|no|NO) false;; \
@@ -569,6 +572,9 @@ t_004_DEPENDENCIES = ../lib/libhawk.la
 t_005_SOURCES = t-005.c t.h
 t_005_LDADD = -lhawk $(LDADD)
 t_005_DEPENDENCIES = ../lib/libhawk.la
+t_006_SOURCES = t-006.c t.h
+t_006_LDADD = -lhawk $(LDADD)
+t_006_DEPENDENCIES = ../lib/libhawk.la
 TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 TEST_EXTENSIONS = .hawk
 HAWK_LOG_COMPILER = ../bin/hawk
@@ -636,6 +642,10 @@ t-005$(EXEEXT): $(t_005_OBJECTS) $(t_005_DEPENDENCIES) $(EXTRA_t_005_DEPENDENCIE
 	@rm -f t-005$(EXEEXT)
 	$(AM_V_CCLD)$(LINK) $(t_005_OBJECTS) $(t_005_LDADD) $(LIBS)
 
+t-006$(EXEEXT): $(t_006_OBJECTS) $(t_006_DEPENDENCIES) $(EXTRA_t_006_DEPENDENCIES) 
+	@rm -f t-006$(EXEEXT)
+	$(AM_V_CCLD)$(LINK) $(t_006_OBJECTS) $(t_006_LDADD) $(LIBS)
+
 mostlyclean-compile:
 	-rm -f *.$(OBJEXT)
 
@@ -647,6 +657,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/t-003.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/t-004.Po@am__quote@ # am--include-marker
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/t-005.Po@am__quote@ # am--include-marker
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/t-006.Po@am__quote@ # am--include-marker
 
 $(am__depfiles_remade):
 	@$(MKDIR_P) $(@D)
@@ -912,6 +923,13 @@ t-005.log: t-005$(EXEEXT)
 	--log-file $$b.log --trs-file $$b.trs \
 	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \
 	"$$tst" $(AM_TESTS_FD_REDIRECT)
+t-006.log: t-006$(EXEEXT)
+	@p='t-006$(EXEEXT)'; \
+	b='t-006'; \
+	$(am__check_pre) $(LOG_DRIVER) --test-name "$$f" \
+	--log-file $$b.log --trs-file $$b.trs \
+	$(am__common_driver_flags) $(AM_LOG_DRIVER_FLAGS) $(LOG_DRIVER_FLAGS) -- $(LOG_COMPILE) \
+	"$$tst" $(AM_TESTS_FD_REDIRECT)
 .hawk.log:
 	@p='$<'; \
 	$(am__set_b); \
@@ -1010,6 +1028,7 @@ distclean: distclean-am
 	-rm -f ./$(DEPDIR)/t-003.Po
 	-rm -f ./$(DEPDIR)/t-004.Po
 	-rm -f ./$(DEPDIR)/t-005.Po
+	-rm -f ./$(DEPDIR)/t-006.Po
 	-rm -f Makefile
 distclean-am: clean-am distclean-compile distclean-generic \
 	distclean-tags
@@ -1060,6 +1079,7 @@ maintainer-clean: maintainer-clean-am
 	-rm -f ./$(DEPDIR)/t-003.Po
 	-rm -f ./$(DEPDIR)/t-004.Po
 	-rm -f ./$(DEPDIR)/t-005.Po
+	-rm -f ./$(DEPDIR)/t-006.Po
 	-rm -f Makefile
 maintainer-clean-am: distclean-am maintainer-clean-generic
 
diff --git a/hawk/t/t-006.c b/hawk/t/t-006.c
new file mode 100644
index 00000000..1ae32285
--- /dev/null
+++ b/hawk/t/t-006.c
@@ -0,0 +1,80 @@
+
+#include <hawk-utl.h>
+#include <stdio.h>
+#include "t.h"
+
+
+struct
+{
+	hawk_ntime_sec_t s1;
+	hawk_ntime_nsec_t ns1;
+	hawk_ntime_sec_t s2;
+	hawk_ntime_nsec_t ns2;
+
+	hawk_ntime_sec_t add_s;
+	hawk_ntime_nsec_t add_ns;
+	hawk_ntime_sec_t sub_s;
+	hawk_ntime_nsec_t sub_ns;
+} tab[] = 
+{
+	{ 12345678,  HAWK_NSECS_PER_SEC - 1,
+	  0,  10,
+          12345679,  9,
+          12345678,  HAWK_NSECS_PER_SEC - 11 },
+
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,
+	  0, 0,  
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), 0, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), 0  },
+
+	{ HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
+	  0, 0,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0  },
+
+	{ 0, 0,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1  },
+
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,
+	  1, 0,  
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1, 
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t) - 1, 0  },
+
+	{ HAWK_TYPE_MAX(hawk_ntime_sec_t), 0,
+	  HAWK_TYPE_MIN(hawk_ntime_sec_t), 0,  
+	  -1, 0,
+	  HAWK_TYPE_MAX(hawk_ntime_sec_t), HAWK_NSECS_PER_SEC - 1  }
+};
+
+int main ()
+{
+	hawk_ntime_t x, y, z;
+	int i;
+	char buf[64];
+
+	for (i = 0; i < HAWK_COUNTOF(tab); i++)
+	{
+		sprintf (buf, "test index %d", i);
+
+		x.sec = tab[i].s1;
+		x.nsec = tab[i].ns1;
+		y.sec = tab[i].s2;
+		y.nsec = tab[i].ns2;
+
+		hawk_add_ntime (&z, &x, &y);
+		T_ASSERT1 (z.sec == tab[i].add_s, buf);
+		T_ASSERT1 (z.nsec == tab[i].add_ns, buf);
+
+		hawk_sub_ntime (&z, &x, &y);
+		T_ASSERT1 (z.sec == tab[i].sub_s, buf);
+		T_ASSERT1 (z.nsec == tab[i].sub_ns, buf);
+
+	}
+
+	return 0;
+
+oops:
+	return -1;
+}