European datestyle

Hi;
I've needed to change the variable DateStyle to European conventions with the
SET command.
But when I restart the psql client, the datestyle is again 'non-european
conventions". How could I force to use the european datestyle always.
(I also use Access2000 as a client. Up to the date, I use three integer
fields for year, months and days to have no problem, but I would like to use
normal dates). So. How can I be sure that the server always understand
'european dates'?
(aaaa-mm-dd)

Thanks and regards

Javier