diff --git a/man5/proc.5 b/man5/proc.5
index 3094d26f0..024e6ea9c 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -1604,7 +1604,9 @@ entries include:
 .TP
 \fIcpu  3357 0 4313 1362393\fP
 The amount of time, measured in units of
-USER_HZ (1/100ths of a second on most architectures),
+USER_HZ (1/100ths of a second on most architectures, use
+.IR sysconf(_SC_CLK_TCK)
+to obtain the right value),
 .\" 1024 on Alpha and ia64
 that the system spent in user mode,
 user mode with low priority (nice), system mode, and the
@@ -2445,6 +2447,7 @@ of thing that needs to be updated very often.
 .BR syslog (2),
 .BR slabinfo (5),
 .BR hier (7),
+.BR time (7),
 .BR arp (8),
 .BR dmesg (8),
 .BR hdparm (8),