diff --git a/builtin_interfaces/msg/Duration.msg b/builtin_interfaces/msg/Duration.msg
index 1311316d..fab5e4fe 100644
--- a/builtin_interfaces/msg/Duration.msg
+++ b/builtin_interfaces/msg/Duration.msg
@@ -1,5 +1,6 @@
-# Duration defines a period between two time points. It is comprised of a
-# seconds component and a nanoseconds component.
+# Duration defines a period between two time points.
+# Messages of this datatype are of ROS Time following this design:
+# https://design.ros2.org/articles/clock_and_time.html
 
 # Seconds component, range is valid over any possible int32 value.
 int32 sec
diff --git a/builtin_interfaces/msg/Time.msg b/builtin_interfaces/msg/Time.msg
index bf710f14..874f15e0 100644
--- a/builtin_interfaces/msg/Time.msg
+++ b/builtin_interfaces/msg/Time.msg
@@ -1,4 +1,5 @@
-# Time indicates a specific point in time, relative to a clock's 0 point.
+# This message communicates ROS Time defined here:
+# https://design.ros2.org/articles/clock_and_time.html
 
 # The seconds component, valid over all int32 values.
 int32 sec