Logical Mistake With Date Function

Hi so what i want to say at the beginning i know that the syntax for setMonth() is from 0 - 11. So what i want to do is i have a drop down menu. there you can choose between novemb

Solution 1:

I just ran this code

var advent = newDate();
advent.setMonth(10);
alert(advent.getMonth());

and it alerted 11.

Why?

Because today is the 31st of the month. Run it again tomorrow and it won't do this.

You create today's date (31st March), and change the month to November. But of course, 31st November does not exist. When you give invalid values to the JavaScript Date object, the date gets 'rolled' forwards. So after calling setMonth your date advent actually contains the date 1st December.

I would recommend creating the date in one go, so advent never has an invalid intermediate date that gets rolled forward:

var advent =newDate(newDate().getYear(), month-1, day);