How do I change the default quaters in PL/SQL

[Quoted] I am writing a pl/sql program and in the program I have to seperate the date in quaters. I know there is a way to do that:

SQL> select * from tempe;

TDATE

26-DEC-2005
26-MAR-2006
01-JAN-2006

SQL> select to_char(tdate, 'YYYY-Q') from tempe;

TO_CHA

2005-4
2006-1
2006-1

but the problem here is our quaters are different from the default [Quoted] quaters. Our quaters start from Mon and ends in Sun. If a month ends in a wed the previous sunday is used as end-date and moday is used for the next quater.
Example:

Moday Dec-26-05 - Sunday Mar-26-06 - 1st quater
Moday Mar-27-06 - Sunday Jun-25-06 - 2nd quater
Moday Jun-26-06 - Sunday Sep-24-06 - 3rd quater
Moday Sep-25-06 - Sunday Dec-3106 - 4th quater

so the first record in the tempe should be 1st quater of 06 according to our busines rule. How do I do that. Your kindness in helping me is greatly appreciated.
Thanks,

Joe Received on Fri Jun 02 2006 - 17:05:29 CEST