How to make the month change when displaying tomorrow's date (now September 33)?

Question

JavaScript

How, when adding several days, set the transition to the next month, since it currently displays September 33?
https://jsfiddle.net/u1jsx7bo/3/

Data = new Date();
Month = Data.getMonth();
Day = Data.getDate() + 17;
switch (Month)
{
  case 0: fMonth="января"; break;
.......
  case 11: fMonth="декабря"; break;
}
document.write("Завтра "+Day+" "+fMonth+" года");

Answer 1

https://jsfiddle.net/1952gjk7/

Answer 2

First Google issue: https://stackoverflow.com/questions/563406/add-day...