I would do this in the DBMS.
Assuming PL/SQL

procedure foo ( Xday number ) is
    nmatch number := 0;
begin

select count(*) into nmatchs
from Whatever a
where trunc(a.theDBdate + Xday) = trunc(sysdate);

if nmatch > 0 then
     callSomeFunction();
end if; 
end;
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This assumes that the function you are calling
is a stored function, and your DB is oracle and
well ... it assumes a lot. But I think it is fair
to ask why not do this with a SQL query?

I don't know ... sorry if this isn't the
answer you are looking for but sometimes
you can't beat a good select statement.

--
Its like a dog that can sing and dance.
It's remarkable because it can do it.
Not that it can do it well.