Missed that you wanted to be able to set date. Then try this:
App.DateField = Ember.TextField.extend({
type: 'date',
date: function(key, date) {
if (date) {
this.set('value', date.toISOString().substring(0, 10));
} else {
value = this.get('value');
if (value) {
date = new Date(value);
} else {
date = null;
}
}
return date;
}.property('value')
});
See example at http://jsbin.com/ulapuf/6/edit