diff --git sys/kern/kern_event.c sys/kern/kern_event.c
index 72386e0..cd6076e 100644
--- sys/kern/kern_event.c
+++ sys/kern/kern_event.c
@@ -529,14 +529,24 @@ knote_fork(struct knlist *list, int pid)
  * interval timer support code.
  */
 static __inline sbintime_t
-timer2sbintime(intptr_t data)
+timer2sbintime(intptr_t data, int flags)
 {
+	sbintime_t modifier;
+
+	modifier = SBT_1MS;
+
+	if (flags & NOTE_SECONDS)
+		modifier = SBT_1S;
+	else if (flags & NOTE_USECONDS)
+		modifier = SBT_1US;
+	else if (flags & NOTE_NSECONDS)
+		modifier = SBT_1NS;
 
 #ifdef __LP64__
-	if (data > INT64_MAX / SBT_1MS)
+	if (data > INT64_MAX / modifier)
 		return INT64_MAX;
 #endif
-	return (SBT_1MS * data);
+	return (modifier * data);
 }
 
 static void
@@ -544,16 +554,20 @@ filt_timerexpire(void *knx)
 {
 	struct callout *calloutp;
 	struct knote *kn;
+	int flag;
 
 	kn = knx;
 	kn->kn_data++;
 	KNOTE_ACTIVATE(kn, 0);	/* XXX - handle locking */
+	flag = 0;
 
 	if ((kn->kn_flags & EV_ONESHOT) != EV_ONESHOT) {
 		calloutp = (struct callout *)kn->kn_hook;
+		if ((kn->kn_sfflags & NOTE_MONOTONIC) == NOTE_MONOTONIC)
+			flag = C_ABSOLUTE;
 		callout_reset_sbt_on(calloutp,
-		    timer2sbintime(kn->kn_sdata), 0 /* 1ms? */,
-		    filt_timerexpire, kn, PCPU_GET(cpuid), 0);
+		    timer2sbintime(kn->kn_sdata, kn->kn_sfflags), 0 /* 1ms? */,
+		    filt_timerexpire, kn, PCPU_GET(cpuid), flag);
 	}
 }
 
@@ -564,17 +578,32 @@ static int
 filt_timerattach(struct knote *kn)
 {
 	struct callout *calloutp;
+	struct timespec ts;
 	sbintime_t to;
+	int64_t now;
+	int flag;
 	unsigned int ncallouts;
 
 	if ((intptr_t)kn->kn_sdata < 0)
 		return (EINVAL);
 	if ((intptr_t)kn->kn_sdata == 0 && (kn->kn_flags & EV_ONESHOT) == 0)
 		kn->kn_sdata = 1;
-	to = timer2sbintime(kn->kn_sdata);
+	to = timer2sbintime(kn->kn_sdata, kn->kn_sfflags);
 	if (to < 0)
 		return (EINVAL);
 
+	if ((kn->kn_sfflags & NOTE_MONOTONIC) == NOTE_MONOTONIC) {
+		if ((kn->kn_flags & EV_ONESHOT) == 0)
+			return (EINVAL);
+		nanouptime(&ts);
+		now = ((ts.tv_sec * 1000000000) + ts.tv_nsec);
+		if (to <= timer2sbintime(now, NOTE_NSECONDS)) {
+			kn->kn_data++;
+			KNOTE_ACTIVATE(kn, 0);	/* XXX - handle locking */
+			return(0);
+		}
+	}
+
 	ncallouts = atomic_load_explicit(&kq_ncallouts, memory_order_relaxed);
 	do {
 		if (ncallouts >= kq_calloutmax)
@@ -588,8 +617,11 @@ filt_timerattach(struct knote *kn)
 	calloutp = malloc(sizeof(*calloutp), M_KQUEUE, M_WAITOK);
 	callout_init(calloutp, CALLOUT_MPSAFE);
 	kn->kn_hook = calloutp;
+	flag = 0;
+	if ((kn->kn_sfflags & NOTE_MONOTONIC) == NOTE_MONOTONIC)
+		flag = C_ABSOLUTE;
 	callout_reset_sbt_on(calloutp, to, 0 /* 1ms? */,
-	    filt_timerexpire, kn, PCPU_GET(cpuid), 0);
+	    filt_timerexpire, kn, PCPU_GET(cpuid), flag);
 
 	return (0);
 }
diff --git sys/sys/event.h sys/sys/event.h
index bad8c9e..28ed84a 100644
--- sys/sys/event.h
+++ sys/sys/event.h
@@ -133,6 +133,12 @@ struct kevent {
 #define	NOTE_TRACKERR	0x00000002		/* could not track child */
 #define	NOTE_CHILD	0x00000004		/* am a child process */
 
+/* additional flags for EVFILT_TIMER */
+#define NOTE_SECONDS	0x00000001		/* data is seconds */
+#define NOTE_USECONDS	0x00000002		/* data is microseconds */
+#define NOTE_NSECONDS	0x00000004		/* data is nanoseconds */
+#define NOTE_MONOTONIC	0x00000008		/* absolute time since boot */
+
 struct knote;
 SLIST_HEAD(klist, knote);
 struct kqueue;