Go home Javascript Date, you are drunk

We had a little problem with some Javascript tests, today July 31.

We were doing this:

var date = new Date();
date.setYear(2013);   
date.setMonth(5);
date.setDate(13);

The variable date supposed to be "13 Jun 2013" but instead today was "13 Jul 2013".

Why?

Because in Javascript when you do setMonth without specifying the day, Javascript takes by default the current day. Today is 31. June 31 doesn't exists. To correct this overflow, Javascript jumps to the next month.

Thats why it was displaying "13 Jul 2013"

Go home Javascript date. You are drunk.