Javascript JSON Date parse in IE7/IE8 returns NaN

Question

I'm parsing a date from a JSON event feed - but the date shows "NaN" in IE7/8:

// Variable from JSON feed (using JQuery's $.getJSON)
var start_time = '2012-06-24T17:00:00-07:00';

// How I'm currently extracting the Month & Day
var d = new Date(start_time);
var month = d.getMonth();
var day = d.getDate();

document.write(month+'/'+day);// "6/24" in most browsers, "Nan/Nan" in IE7/8

What am I doing wrong? Thanks!

Answer 1

In older browsers, you can write a function that will parse the string for you.

This one creates a Date.fromISO method- if the browser can natively get the correct date from an ISO string, the native method is used.

Some browsers got it partly right, but returned the wrong timezone, so just checking for NaN may not do.

Polyfill:

(function(){
    var D= new Date('2011-06-02T09:34:29+02:00');
    if(!D || +D!== 1307000069000){
        Date.fromISO= function(s){
            var day, tz,
            rx=/^(\d{4}\-\d\d\-\d\d([tT ][\d:\.]*)?)([zZ]|([+\-])(\d\d):(\d\d))?$/,
            p= rx.exec(s) || [];
            if(p[1]){
                day= p[1].split(/\D/);
                for(var i= 0, L= day.length; i<L; i++){
                    day[i]= parseInt(day[i], 10) || 0;
                };
                day[1]-= 1;
                day= new Date(Date.UTC.apply(Date, day));
                if(!day.getDate()) return NaN;
                if(p[5]){
                    tz= (parseInt(p[5], 10)*60);
                    if(p[6]) tz+= parseInt(p[6], 10);
                    if(p[4]== '+') tz*= -1;
                    if(tz) day.setUTCMinutes(day.getUTCMinutes()+ tz);
                }
                return day;
            }
            return NaN;
        }
    }
    else{
        Date.fromISO= function(s){
            return new Date(s);
        }
    }
})()

Result:

var start_time = '2012-06-24T17:00:00-07:00';
var d =  Date.fromISO(start_time);
var month = d.getMonth();
var day = d.getDate();

alert(++month+' '+day); // returns months from 1-12