I can't see why it's not working, if the previous sub worked, since they both seem to be performing the same function on different tables. But you could try putting the date format into the date_get to see whether it makes any difference - I have had to do this when working on the Clicktrack table.
my $delete_by = GT::Date::date_get ( time() - 172800, '%yyyy%%mm%%dd%%HH%%MM%%ss%' );
my $delete_by = GT::Date::date_get ( time() - 172800, '%yyyy%%mm%%dd%%HH%%MM%%ss%' );
