Shell Programming and Scripting

Hi all,
All I need to do is
calculate the system date to my desire date.

My case is
everyday in my system , it will receive ftp file from another unix server.

If I issued 'date' for today it will return this :
-bash-3.00$ date +%Y%m%d
20070605

but the ftp file that receive everyday is like this
birth_20070604.dat

see?
because this ftp file is less than today for 1 day.
I want to use this file to process to another job to execute this file .
So,I want to minus 1 day from system date that I got from 'date' function

BTW,I use solaris 10
when I use date -d
it said somethings like
illegal option -d

Thank you very much in advance


........................................................................................

Sorry Let me change my question
After I look backward through these forums
I found that they have some kind of this

DATE_STAMP=`TZ=CST+24 date +%Y%m%d`
echo $DATE_STAMP
20070604

So I can get a yesterday date already
but another problem is
A year format

I want to convert Christian era to Buddhist Era
That means
If I want to convert by mathematic
I need to +543 from current Christian era
eg. If want to change to Buddhist Era,I need to plus 543 to 2007
So, the Buddhist Era of this year is 2007+543 = 2550

Code:

eval DATE_STAMP=$(TZ=CST+24 date +'$((%Y+543))%m%d')

Jean-Pierre.