diff --git a/lib/isc/include/isc/result.h b/lib/isc/include/isc/result.h
index 246aefb..0007543 100644
--- a/lib/isc/include/isc/result.h
+++ b/lib/isc/include/isc/result.h
@@ -83,9 +83,9 @@
 #define ISC_R_UNSET			61	/*%< unset */
 #define ISC_R_MULTIPLE			62	/*%< multiple */
 #define ISC_R_WOULDBLOCK		63	/*%< would block */
-
+#define ISC_R_TIMESHIFTED               64      /*%< system time changed */
 /*% Not a result code: the number of results. */
-#define ISC_R_NRESULTS 			64
+#define ISC_R_NRESULTS 			66
 
 ISC_LANG_BEGINDECLS
 
diff --git a/lib/isc/include/isc/util.h b/lib/isc/include/isc/util.h
index 332dc0c..f81967d 100644
--- a/lib/isc/include/isc/util.h
+++ b/lib/isc/include/isc/util.h
@@ -233,6 +233,10 @@
  * Time
  */
 #define TIME_NOW(tp) 	RUNTIME_CHECK(isc_time_now((tp)) == ISC_R_SUCCESS)
+#ifdef CLOCK_BOOTTIME
+#define TIME_MONOTONIC(tp) 	RUNTIME_CHECK(isc_time_boottime((tp)) == ISC_R_SUCCESS)
+#endif
+
 
 /*%
  * Misc
diff --git a/lib/isc/result.c b/lib/isc/result.c
index a707c32..6776fc6 100644
--- a/lib/isc/result.c
+++ b/lib/isc/result.c
@@ -99,6 +99,7 @@ static const char *description[ISC_R_NRESULTS] = {
 	"unset",				/*%< 61 */
 	"multiple",				/*%< 62 */
 	"would block",				/*%< 63 */
+        "time changed",                         /*%< 64 */
 };
 
 static const char *identifier[ISC_R_NRESULTS] = {
@@ -166,6 +167,7 @@ static const char *identifier[ISC_R_NRESULTS] = {
 	"ISC_R_UNSET",
 	"ISC_R_MULTIPLE",
 	"ISC_R_WOULDBLOCK",
+        "ISC_R_TIMESHIFTED",
 };
 
 #define ISC_RESULT_RESULTSET			2
diff --git a/lib/isc/unix/app.c b/lib/isc/unix/app.c
index bace2bd..e9814d2 100644
--- a/lib/isc/unix/app.c
+++ b/lib/isc/unix/app.c
@@ -441,15 +441,51 @@ isc__app_ctxonrun(isc_appctx_t *ctx0, isc_mem_t *mctx, isc_task_t *task,
 static isc_result_t
 evloop(isc__appctx_t *ctx) {
 	isc_result_t result;
+        isc_time_t now;
+#ifdef CLOCK_BOOTTIME
+        isc_time_t monotonic;
+        isc_uint64_t diff  = 0;
+#else
+        isc_time_t prev;
+        TIME_NOW(&prev);
+#endif
+
+
+
 
 	while (!ctx->want_shutdown) {
 		int n;
-		isc_time_t when, now;
+		isc_time_t when;
+                
 		struct timeval tv, *tvp;
 		isc_socketwait_t *swait;
 		isc_boolean_t readytasks;
 		isc_boolean_t call_timer_dispatch = ISC_FALSE;
 
+                isc_uint64_t us; 
+
+#ifdef CLOCK_BOOTTIME
+                // TBD macros for following three lines
+                TIME_NOW(&now);
+                TIME_MONOTONIC(&monotonic);
+                // INSIST(now.seconds > monotonic.seconds) 
+                us = isc_time_microdiff (&now, &monotonic);
+                if (us < diff){ 
+                  us = diff - us;
+                  if (us > 1000000){ // ignoring shifts less than one second
+                    return ISC_R_TIMESHIFTED;
+                  };
+                  diff = isc_time_microdiff (&now, &monotonic);
+                } else {
+                  diff = isc_time_microdiff (&now, &monotonic);
+                  // not implemented
+                }
+#else
+                TIME_NOW(&now);
+                if (isc_time_compare (&now, &prev) < 0)
+                  return ISC_R_TIMESHIFTED;
+                TIME_NOW(&prev);
+#endif                
 		/*
 		 * Check the reload (or suspend) case first for exiting the
 		 * loop as fast as possible in case:
@@ -474,9 +510,10 @@ evloop(isc__appctx_t *ctx) {
 			if (result != ISC_R_SUCCESS)
 				tvp = NULL;
 			else {
-				isc_uint64_t us;
+
 
 				TIME_NOW(&now);
+
 				us = isc_time_microdiff(&when, &now);
 				if (us == 0)
 					call_timer_dispatch = ISC_TRUE;
diff --git a/lib/isc/unix/include/isc/time.h b/lib/isc/unix/include/isc/time.h
index 75e24b9..de8b399 100644
--- a/lib/isc/unix/include/isc/time.h
+++ b/lib/isc/unix/include/isc/time.h
@@ -129,6 +129,26 @@ isc_time_isepoch(const isc_time_t *t);
  *\li	't' is a valid pointer.
  */
 
+#ifdef CLOCK_BOOTTIME
+isc_result_t
+isc_time_boottime(isc_time_t *t);
+/*%<
+ * Set 't' to monotonic time from previous boot
+ * it's not affected by system time change. It also
+ * includes the time system was suspended
+ *
+ * Requires:
+ *\li	't' is a valid pointer.
+ *
+ * Returns:
+ *
+ *\li	Success
+ *\li	Unexpected error
+ *		Getting the time from the system failed.
+ */
+#endif /* CLOCK_BOOTTIME */
+ 
+
 isc_result_t
 isc_time_now(isc_time_t *t);
 /*%<
diff --git a/lib/isc/unix/time.c b/lib/isc/unix/time.c
index 2210240..d7613b8 100644
--- a/lib/isc/unix/time.c
+++ b/lib/isc/unix/time.c
@@ -496,3 +496,25 @@ isc_time_formatISO8601ms(const isc_time_t *t, char *buf, unsigned int len) {
 			 t->nanoseconds / NS_PER_MS);
 	}
 }
+
+
+#ifdef CLOCK_BOOTTIME
+isc_result_t
+isc_time_boottime(isc_time_t *t) {
+  struct timespec ts;
+  
+  char strbuf[ISC_STRERRORSIZE];
+
+  if (clock_gettime (CLOCK_BOOTTIME, &ts) != 0){
+    isc__strerror(errno, strbuf, sizeof(strbuf));
+    UNEXPECTED_ERROR(__FILE__, __LINE__, "%s", strbuf);
+    return (ISC_R_UNEXPECTED);    
+  }
+
+  t->seconds = ts.tv_sec;
+  t->nanoseconds = ts.tv_nsec;
+
+  return (ISC_R_SUCCESS);
+  
+};
+#endif