looking for user's timezone

tz.js

var cookie_tz = $.cookie('tz');
    if (user_tz == null) {
        if (cookie_tz == null) {
            try {
                var tmp_tz = jstz.determine_timezone();
                if (tmp_tz) {
                    user_tz = tmp_tz.name();
                    $.cookie('tz', user_tz);
                }
            } catch(err) {
                console.log('failed to determine timezone');
            }
        } else {
            user_tz = cookie_tz;
        }
    } else {
        if (cookie_tz == null) {
            $.cookie('tz', user_tz);
        }
    }