How to create recurrence schedule event?

Hi,

I am trying to port sybase codes to posgresql. I have looked into the postgresql documentation

but couldn't find good information on how to  create an equivalent recurrence event

which similar to the sybase codes below.

Can some one please help?

sybase codes:

create event PURGE_ORDER schedule

start time '00:00:00' every 30 minutes

       on ( 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday','Saturday', 'Sunday' )

handler begin

     declare @value           varchar(128);

     call cleanup_order();

end;

Thanks,

QT