create or replace function date_tz_convert( 
  p_date      date, 
  p_from_tz   varchar2, 
  p_to_tz     varchar2 
) 
  return date 
is 
begin 
  return cast(from_tz(cast(p_date as timestamp), p_from_tz) at time zone p_to_tz as date); 
end date_tz_convert;