diff --git a/clock/clock.go b/clock/clock.go
index 591563a1..a2083019 100644
--- a/clock/clock.go
+++ b/clock/clock.go
@@ -20,6 +20,10 @@ import (
 // negative values. However, for such lengths of time, a fixed 24 hours per day
 // is assumed and a modulo operation Mod24 is provided to discard whole multiples of 24 hours.
 //
+// Clock is a type of integer (actually int32), so values can be compared and sorted as
+// per other integers. The constants Second, Minute, Hour and Day can be added and subtracted
+// with obvious outcomes.
+//
 // See https://en.wikipedia.org/wiki/ISO_8601#Times
 type Clock int32
 
diff --git a/clock/clock_test.go b/clock/clock_test.go
index e9bdc675..0d629167 100644
--- a/clock/clock_test.go
+++ b/clock/clock_test.go
@@ -269,6 +269,8 @@ func TestClockParseGoods(t *testing.T) {
 		{"01:00", New(1, 0, 0, 0)},
 		{"01:02", New(1, 2, 0, 0)},
 		{"23:59", New(23, 59, 0, 0)},
+		{"0911", New(9, 11, 0, 0)},
+		{"1024", New(10, 24, 0, 0)},
 		{"2359", New(23, 59, 0, 0)},
 		{"00:00:00", New(0, 0, 0, 0)},
 		{"00:00:01", New(0, 0, 1, 0)},
@@ -297,10 +299,14 @@ func TestClockParseGoods(t *testing.T) {
 		{"1am", New(1, 0, 0, 0)},
 		{"1pm", New(13, 0, 0, 0)},
 		{"1:00am", New(1, 0, 0, 0)},
-		{"1:00pm", New(13, 0, 0, 0)},
+		{"1:23am", New(1, 23, 0, 0)},
+		{"1:23pm", New(13, 23, 0, 0)},
+		{"01:23pm", New(13, 23, 0, 0)},
 		{"1:00:00am", New(1, 0, 0, 0)},
 		{"1:02:03pm", New(13, 2, 3, 0)},
+		{"01:02:03pm", New(13, 2, 3, 0)},
 		{"1:02:03.004pm", New(13, 2, 3, 4)},
+		{"01:02:03.004pm", New(13, 2, 3, 4)},
 		{"1:20:30.04pm", New(13, 20, 30, 40)},
 		{"1:20:30.4pm", New(13, 20, 30, 400)},
 		{"1:20:30.pm", New(13, 20, 30, 0)},