Why aren't you doing the date calculation in the database? That way you would only need to calculate the start and end date in Perl, or, if your database has date calculation functions, not even that:

$sth = $dbh->prepare(<<SQL);
    
    SELECT * FROM mytable
    WHERE mydate between ? and ?
    ORDER BY mydate ASC
SQL

$sth->execute($start_date, $end_date);
my $res = $sth->fetchall_arrayref;
[download]

$sth = $dbh->prepare(<<SQL);
    
    SELECT * FROM mytable
    WHERE ? - mydate <= 15 -- this should really use the date/time fun
+ctions instead
    ORDER BY mydate ASC
SQL

$sth->execute($end_date);
my $res = $sth->fetchall_arrayref;
[download]