code goes here
Much better looking than quotes or pre alone.
set until time "to_date('03/29/2010 08:00:00','MM/DD/YYYY HH24:MI:SS')";
You can take this a step further in complication with anything for dates, such as cloning to the most recent archivelog backup (assuming a scheduled archive log backup takes place every hour at 35 after)
set until time "sysdate - 1/24";
set until time "trunc((sysdate - 30/1440),'HH24')+30/1440";
diff PROD/compile-prod.log <(sed 's/TEST/PROD/g' ../TEST/compile-test.log