MS SQL "isDate" equivalent in plpgsql?

Hi,

I am not sure if this is the right newsgroup. If not, please excuse, I
didn't find one, that'ld fit better. *g*

I am porting from MS SQL 7.0 to PostgreSQL. In one Stored Procedure the
function "isDate" is used. IsDate determines, whether the input string is a
date or not:

select isdate('05.15.2003');
Result: 1
select isdate('foobar');
Result: 0

Is there a function in plpgsql like that?
Maybe someone has a self-written function that implements that?

Thanks in advance and regards,
Daniel