dojox.calendar.calendar startTimeAttr not work

[vtsuper]

it works perfect in the following case.

var store = new Observable(new Memory({data: [
	{"id":1,"summary":"event1","startTime":"2015-01-12T10:00:00.000","endTime":"2015-01-12T11:00:00.000"},
	{"id":2,"summary":"event2","startTime":"2015-01-13T10:00:00.000","endTime":"2015-01-13T11:00:00.000"
]}));

new Calendar({
	decodeDate: function(s){return stamp.fromISOString(s);},
	encodeDate: function(d){return stamp.toISOString(d);},
});

but it fail once I change the startTimeAttr and endTimeAttr like this.

var store = new Observable(new Memory({data: [
	{"id":1,"summary":"event1","begin":"2015-01-12T10:00:00.000","end":"2015-01-12T11:00:00.000"},
	{"id":2,"summary":"event2","begin":"2015-01-13T10:00:00.000","end":"2015-01-13T11:00:00.000"
]}));

new Calendar({
	startTimeAttr: "begin",
	endTimeAttr: "end",
	decodeDate: function(s){return stamp.fromISOString(s);},
	encodeDate: function(d){return stamp.toISOString(d);}
});
}}})

[vtsuper]

firebug produce this error