>Dear Dragan Nedeljkowich
>
>Thank for your reply,
>I try your solution, but I find that the invoice date 24 Apr 14 will deduct 1 day and as the result
>become to 23 Apr 14
>
>What wrong ?

I can't test. I suppose I was off by one. Just add a +1 at the end of the line where the date is assigned, or change the offset date to one day earlier (i.e. date(1899,12,30).