Added more comments to the test cases.

mysql-test/t/date_formats.test

@@ -280,6 +280,10 @@ select str_to_date( 1, IF(1=1,NULL,NULL) );
 
 #
 # Bug#11326
+# TIME_FORMAT using "%r" returns wrong hour using 24:00:00 in TIME column
+#
+# This tests that 24:00:00 does not return PM, when it should be AM.
+# Some other values are being tested same time.
 #
 
 SELECT TIME_FORMAT("24:00:00", '%r');
@@ -291,6 +295,10 @@ SELECT TIME_FORMAT("25:00:00", '%r');
 
 #
 # Bug#11324
+# TIME_FORMAT using "%l:%i" returns 36:00 with 24:00:00 in TIME column
+#
+# This tests that 24:00:00 does not change to "36:00 AM". Testing
+# some other values same time.
 #
 
 SELECT TIME_FORMAT("00:00:00", '%l %p');