[mythtv-users] Understanding custom recording advanced examples, interval 2 hour?

[catfish]

I'm playing with Custom Recording and using the Examples shown in the 
wiki for Daily Show. I was able to locate an archive of the discussion 
that works on (close to) this example at
http://www.gossamer-threads.com/lists/mythtv/users/153882

"
program.title LIKE "%Daily Show%"
AND MINUTE(program.starttime) = 0
AND HOUR(DATE_SUB(program.starttime, INTERVAL 2 HOUR)) > 20
AND WEEKDAY(DATE_SUB(program.starttime, INTERVAL 2 HOUR)) < 4
AND (WEEKDAY(DATE_SUB(program.starttime, INTERVAL 2 HOUR)) = 0
OR program.previouslyshown = 0)

Any "Daily Show" title, on the hour, whose start time minus two is
in the evening of Monday through Thursday with generics accepted on
Monday but must be new episodes for the rest of the week.
"

What I'm not sure about is why the Interval 2 Hour aka "start time minus 
two is the evening". Why check two hours before the start time if it's 
after 9pm? Why not check if the current hour is => 11pm?