This line:

print " " x ($lenght_date), $count{$_}->{$date[$i]};
[download]

Should be using printf, i.e. something like:

printf "%${lenght_date}s   ", $count{$_}->{$date[$i]};
[download]

Similarly,

print map { sprintf "%7d", $_ } @tasks;
[download]

Should be written as:

print map { sprintf "%${lenght_date}s   " } @tasks;
[download]

In other words, use the same formatting technique, with the same widths, for every row of the output.