arhiving rule

I have, what I think is a simple rule to arrive transactions:

 create rule usageupdt as on update to usage
           do insert into usageHistory
              (lkey, jan, feb, mar, bowner, penalty, prepay, bal, notes,
change)
           values
              (new.lkey, old.jan, old.feb, old.mar, old.bowner,
               old.penalty, old.prepay, old.bal, old.notes, 'now')


the only problem is that once is rule is created,  new rows in the
archive table all have the same date!
         -the date when the rule was created....


    thanks
    art