Jquery UI Datepicker disabling wrong days - jquery-ui

Question

I have run in to issue that days that have to be disabled are shifted to the next day.
The idea is that day that does not exist in our booking object or have a value less than 1 should be disabled on calendar.
here is simplified version of my script and demonstration on jsfiddle:
var bookings = {
"2012-09-01": 24,
"2012-09-03": 31,
"2012-09-05": 27,
"2012-09-06": 9,
"2012-09-07": 18,
"2012-09-08": 0,
"2012-09-10": 20,
"2012-09-12": 19,
"2012-09-13": 0,
"2012-09-14": 9,
"2012-09-15": 24,
"2012-09-17": 19,
"2012-09-19": 28,
"2012-09-20": 15,
"2012-09-21": 12,
"2012-09-22": 25,
"2012-09-24": 19,
"2012-09-26": 0,
"2012-09-27": 0,
"2012-09-28": 0,
"2012-09-29": 0
};
function MyEvent(date)
{
bookings = bookings || {};
this.date = date.toISOString().substr(0, 10);
this.display = (typeof bookings[this.date] == 'number' && bookings[this.date] > 0);
return this;
}
MyEvent.prototype.toArray = function () {
return [this.display, null, null];
};
$(function ()
{
$('#eventCalendar').datepicker({
dateFormat: "yy-mm-dd",
firstDay: 1,
defaultDate: "2012-09-24",
beforeShowDay: function (date)
{
return new MyEvent(date).toArray();
}
}
);
});
Can some one suggest me what am I doing wrong or is it a bug?

Answer 1

It was a little struggle, but is not a bug.
There is a problem using:
date.toISOString()
the operation can return a different date (for example next day) from the original date passed from the plug in, because the function ignores timezone offsets
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date/toISOString
so your condition will not work well.
Here is a working fiddle the is not using that function: http://jsfiddle.net/nBejK/2/