Setting up head of the day columns in the calendar?

[Csanyi Pal]

Hi,

I have installed on Debian GNU/Linux testing/sid
GNU Emacs 24.1.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.10) of
2012-07-20 on trouble, modified by Debian.

I want to be used the first three instead of two characters of each day
string of head of the day columns in the calendar.

My reason is that that in Hungarian we have Calendar Day Name Array:
Sunday: Vasárnap
Monday: Hétfő
Tuesday: Kedd
Wednesday: Szerda
Thursday: Csütörtök
Friday: Péntek
Saturday: Szombat

and one can see abowe the first two character of
Wednesday: Szerda
and
Saturday: Szombat

are 'Sz' so in Calendar I get:
   Július 2012
Hé Ke Sz Cs Pé Sz Va

but I wish to get
   Július 2012
Hét Ked Sze Csü Pén Szo Vas

The side effect (that is bad for me) is that that both Wednesday: Szerda
and Saturday: Szombat are marked in Calendar with red color, along with
Sunday: Vasárnap. 

Can I set up this somehow so I can get a proper display of head of day
columns in the calendar? 

-- 
Regards from Pal