Index: head/include/time.h
===================================================================
--- head/include/time.h
+++ head/include/time.h
@@ -98,12 +98,14 @@
 #endif
 
 /* These macros are also in sys/time.h. */
-#if !defined(CLOCK_REALTIME) && __POSIX_VISIBLE >= 200112
+#if !defined(CLOCK_REALTIME) && __POSIX_VISIBLE >= 199506
 #define CLOCK_REALTIME	0
-#ifdef __BSD_VISIBLE
+#endif /* !defined(CLOCK_REALTIME) && __POSIX_VISIBLE >= 199506 */
+#if !defined(CLOCK_VIRTUAL) && __BSD_VISIBLE
 #define CLOCK_VIRTUAL	1
 #define CLOCK_PROF	2
-#endif
+#endif /* !defined(CLOCK_VIRTUAL) && __BSD_VISIBLE */
+#if !defined(CLOCK_MONOTONIC) && __POSIX_VISIBLE >= 200112
 #define CLOCK_MONOTONIC	4
 #define CLOCK_UPTIME	5		/* FreeBSD-specific. */
 #define CLOCK_UPTIME_PRECISE	7	/* FreeBSD-specific. */
@@ -115,14 +117,14 @@
 #define CLOCK_SECOND	13		/* FreeBSD-specific. */
 #define CLOCK_THREAD_CPUTIME_ID	14
 #define	CLOCK_PROCESS_CPUTIME_ID	15
-#endif /* !defined(CLOCK_REALTIME) && __POSIX_VISIBLE >= 200112 */
+#endif /* !defined(CLOCK_MONOTONIC) && __POSIX_VISIBLE >= 200112 */
 
-#if !defined(TIMER_ABSTIME) && __POSIX_VISIBLE >= 200112
 #if __BSD_VISIBLE
 #define TIMER_RELTIME	0x0	/* relative timer */
 #endif
+#if !defined(TIMER_ABSTIME) && __POSIX_VISIBLE >= 199506
 #define TIMER_ABSTIME	0x1	/* absolute timer */
-#endif /* !defined(TIMER_ABSTIME) && __POSIX_VISIBLE >= 200112 */
+#endif /* !defined(TIMER_ABSTIME) && __POSIX_VISIBLE >= 199506 */
 
 struct tm {
 	int	tm_sec;		/* seconds after the minute [0-60] */
Index: head/sys/sys/time.h
===================================================================
--- head/sys/sys/time.h
+++ head/sys/sys/time.h
@@ -463,8 +463,12 @@
 /* These macros are also in time.h. */
 #ifndef CLOCK_REALTIME
 #define	CLOCK_REALTIME	0
+#endif
+#ifndef CLOCK_VIRTUAL
 #define	CLOCK_VIRTUAL	1
 #define	CLOCK_PROF	2
+#endif
+#ifndef CLOCK_MONOTONIC
 #define	CLOCK_MONOTONIC	4
 #define	CLOCK_UPTIME	5		/* FreeBSD-specific. */
 #define	CLOCK_UPTIME_PRECISE	7	/* FreeBSD-specific. */