[Xymon] trimhistory and "No events received in the last 240 minutes"

[L.M.J]

Hi,

   Since I launched this command "./trimhistory --cutoff=`date +%s 
--date="1 Feb 2011"` --drop --dropsvcs --droplogs --progress"
   I don't have anymore any event displayed in the "Non-green systems" 
page : "No events received in the last 240 minutes" and "No events 
acknowledged in the last 240 minutes"

   Anyones knows why ?

  Thanks