mapping date value (SQL question)

Howdy:

I'm running Postgres 7.1.3 on RedHat Linux 7.2, kernel version
2.4.7 rel 10.

I've created a table which includes the date. I have been instructed
to map the date into something that reflects the quarter of the year
on the fly (somewhere in the script). For example:

(currently) date: (needed) quarter:
2001-02-26 200101
1998-05-12 199802
803-11-11 80304

I was thinking I'd have to use something like a case statement, but
I don't know enough about SQL to do something like that. Somehow, I
had the notion that if it were possible to write 'if-then-else' loops
I could probably do it.

Is there such a mechanism to do what is being asked of me?

Thanks!

-X