diff --git a/include/ucore/ucore_timers.h b/include/ucore/ucore_timers.h
index c950e83..aa08354 100644
--- a/include/ucore/ucore_timers.h
+++ b/include/ucore/ucore_timers.h
@@ -9,6 +9,7 @@
 
 struct UCTimer;
 struct UCTimers;
+struct UCoreClock;
 
 //internal timer states
 enum {
@@ -62,6 +63,7 @@ struct UCTimer {
 /** Timer engine. Must be initialized onnce.*/
 struct UCTimers {
     RBTree timer_tree;
+    struct UCoreClock *uclock;
     size_t seq; //used to generate unique timers
     TAILQ_HEAD(, UCTimer) ready_list; //pending timers to be fired while inside uc_timers_run
 };
@@ -73,6 +75,12 @@ struct UCTimers {
  */
 void uc_timers_init(struct UCTimers *t);
 
+/** Initialize a timer engine for use, with a user supplied clock.
+ *
+ * @param t UCTimers struct to initialize
+ */
+void uc_timers_init_ex(struct UCTimers *t, struct UCoreClock *uclock);
+
 /** Add a (one-shot) timer to the timer engine.
  * User fills in the callback and any cookie members of the UCTimer. The callback
  * will be called when the timer expires, and the timer is removed from the engine
@@ -127,7 +135,7 @@ int uc_timer_running(const struct UCTimer *timer);
  * @return the number of timers fired, or negative if an error occured(presently no errors
  *         are possible and the return value is always >= 0
  **/
-int uc_timers_run(struct UCTimers *timers, const struct timeval *now);
+int uc_timers_run(struct UCTimers *timers);
 
 //uc_timers_destroy(struct UCTimers *timers) is currently missing..
 
diff --git a/src/iomux_impl.c b/src/iomux_impl.c
index e7d7cce..5f0aff5 100644
--- a/src/iomux_impl.c
+++ b/src/iomux_impl.c
@@ -74,10 +74,9 @@ int iomux_run(struct IOMux *mux)
         if (uc_timers_first(&mux->timers, &first_timer) == 0) {
             future_to_interval(&first_timer, &mux->now, &timeout);
             timeoutp = &timeout;
-        /*    fprintf(stdout, "now %d %d future %d %d interval %d %d\n", mux->now.tv_sec, mux->now.tv_usec,
+        /*    TRACEF("now %d %d future %d %d interval %d %d\n", mux->now.tv_sec, mux->now.tv_usec,
                                                               first_timer.tv_sec, first_timer.tv_usec,
                                                               timeout.tv_sec, timeout.tv_usec);
-           fflush(stdout); 
         */  
 
             assert(timeout.tv_sec >= 0);
@@ -101,9 +100,8 @@ int iomux_run(struct IOMux *mux)
 int iomux_timers_run(struct IOMux *mux)
 {
     int event_cnt;
-    gettimeofday(&mux->now, NULL);
 
-    event_cnt = uc_timers_run(&mux->timers, &mux->now);
+    event_cnt = uc_timers_run(&mux->timers);
     assert(event_cnt >= 0);
 
     return event_cnt;
diff --git a/src/ucore_timers.c b/src/ucore_timers.c
index c0751e1..9d25b4d 100644
--- a/src/ucore_timers.c
+++ b/src/ucore_timers.c
@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <ucore/ucore_timers.h>
+#include <ucore/ucore_clock.h>
 
 
 static int timers_cmp(const void *a_, const void *b_)
@@ -35,9 +36,15 @@ static void uc_timer_real_add(struct UCTimers *timers, struct UCTimer *timer)
 }
 
 void uc_timers_init(struct UCTimers *t)
+{
+    uc_timers_init_ex(t, &ucore_timeofday_clock);
+}
+
+void uc_timers_init_ex(struct UCTimers *t, struct UCoreClock *uclock)
 {
     t->timer_tree.node = NULL;
     t->timer_tree.compare = timers_cmp;
+    t->uclock = uclock;
     t->seq = 0;
     TAILQ_INIT(&t->ready_list);
 }
@@ -54,7 +61,7 @@ void uc_timer_add(struct UCTimers *timers, struct UCTimer *timer, int sec, int u
     tmp.tv_sec = sec;
     tmp.tv_usec = usec;
 
-    gettimeofday(&now, NULL); 
+    timers->uclock->now(timers->uclock, &now);
     timeradd(&now, &tmp, &timer->timeout);
     uc_timer_real_add(timers, timer);
 }
@@ -108,10 +115,13 @@ int uc_timer_running(const struct UCTimer *timer)
 }
 
 
-int uc_timers_run(struct UCTimers *timers, const struct timeval *now)
+int uc_timers_run(struct UCTimers *timers)
 {
     RBNode *node;
     int cnt = 0;
+    struct timeval now;
+
+    timers->uclock->now(timers->uclock, &now);
 
     /* First find all the expired nodes, place them in a linked list. 
      * Callbacks cannot be performed here, as the callback might alter
@@ -122,7 +132,7 @@ int uc_timers_run(struct UCTimers *timers, const struct timeval *now)
     for (node = uc_rb_first(&timers->timer_tree); node ; node = uc_rb_next(node)) {
         struct UCTimer *t = node->data;
         //Note, timercmp does not work for >=
-        if (!timercmp(now, &t->timeout, <)) {
+        if (!timercmp(&now, &t->timeout, <)) {
             TAILQ_INSERT_TAIL(&timers->ready_list, t, ready_entry);
             t->state = UC_TIMER_PENDING; //so uc_timer_remove knows
                                          //it have to remove it from the ready_list
@@ -151,7 +161,6 @@ int uc_timers_run(struct UCTimers *timers, const struct timeval *now)
         cnt++;
     }
 
-
     return cnt;
 }
 
diff --git a/test/timers.c b/test/timers.c
index 315cfc6..1c60b65 100644
--- a/test/timers.c
+++ b/test/timers.c
@@ -69,9 +69,7 @@ int main(int argc, char *argv[])
     uc_timer_add(&timers, &my_struct2.timer, 10, 0);
 
     for(;;) {
-        struct timeval now;
-        gettimeofday(&now, NULL);
-        uc_timers_run(&timers, &now);
+        uc_timers_run(&timers);
 #ifndef FULL_SPEED
         usleep(1000);
 #endif