Problem with timestamp field/time function.. (upgrading from 7.0 to 7.2.1)

Hi All:
I've googling around, searching the mailinglist archive and reading FAQ's 
but I haven't find the answer for my question. And I know it is quite 
commom! I'm trying upgrading to 7.2.1.
I'm running postgresql 7.0 with a column like:
                     Table "materia"       Column       |           Type           | Modifiers
--------------------+--------------------------+-----------

materiadata        | timestamp with time zone | not null
mmateriatitulo      | character varying(80)    | not null
materiasequencial  | numeric(30,6)            | not null


I used to execute this query:
select max(time(materiadata)) from materia;

orselect materiasequencial, materiatitulo, time(materiadata)from materiaorder by time(materiadata) desc;    
I've read at PostgreSQL 7.3dev Administrator Guide's Release Notes that 
time() and timestamp() functions in postgresql 7.2 are deprecated (so in 
7.2.1).
So, how can I get the same result above without using time() ??
Or if it not possible, how can I extract (yes, I tried with extract() 
function too) time from a timestamp column?I know it's quite simple question... but I haven't find any clue!


Thanks a lot in advance.
Bests regards



[]'s
Lucas Brasilino
brasilino@recife.pe.gov.br
http://www.recife.pe.gov.br
Emprel -    Empresa Municipal de Informatica (pt_BR)    Municipal Computing Enterprise (en_US)
Recife - Pernambuco - Brasil
Fone: +55-81-34167078