Question

This morning I noticed a peculiar issue with the JavaScript setFullYear method.

When using the method like so:

d.setFullYear(2012,2,8);

The correct value is returned:

Thu Mar 08 2012 10:30:04 GMT+0000 (GMT Standard Time)

However if I use the parseInt method to return the integers, the date returned is incorrect:

d.setFullYear(parseInt("2012"), parseInt("02"), parseInt("08"));

returns:

Wed Feb 29 2012 10:31:30 GMT+0000 (GMT Standard Time)

It appears that the parseInt method is returning the incorrect values, but when I test it:

document.write(parseInt("2"));

Then the correct value is returned (2)

A working fiddle is here: http://jsfiddle.net/rXByJ/

Does the problem lie with parseInt or with setFullYear?

Answer 1

The problem is that parseInt('08') is 0. This works:

d.setFullYear(parseInt("2012"), parseInt("02"), 8);

Both parseInt(’08’) and parseInt(’09’) return zero because the
function tries to determine the correct base for the numerical system
used. In Javascript numbers starting with zero are considered octal
and there’s no 08 or 09 in octal, hence the problem.

http://www.ventanazul.com/webzine/articles/issues-parseint-javascript

Solution is to use the second parameter:

parseInt('08', 10) 

Or

Number('08')

Also see How do I work around JavaScript's parseInt octal behavior?