EPiServer - Nullable date property

Dojo widget

define([
        "dojo/_base/declare",
        "dojo/_base/lang",
        "dojo/dom-style",
        "dojo/dom-construct",
        "dojo/keys",
        "dojo/on",
        "epi/shell/widget/DateTimeSelectorDropDown"
    ],
    function(
        declare,
        lang,
        domStyle,
        domConstruct,
        keys,
        on,
        DateTimeSelectorDropDown
    ) {
        return declare("alloy.editors.nullableDateTimeSelectorDropDown", [DateTimeSelectorDropDown], {
            clearLinkNode: null,

            postMixInProperties: function() {
                this.inherited(arguments);
                this.clearNode = domConstruct.create("a", { innerHTML: "Clear value", title: "CTRL + DEL" });
                domStyle.set(this.clearNode, {
                    'float': 'right',
                    'margin': '-20px -90px 0 0',
                    'cursor': 'pointer'
                });
            },

            postCreate: function() {
                this.inherited(arguments);

                on(this.clearNode, "click", lang.hitch(this, this._clearValue));
                on(this, "keypress", function (evt) {
                    if (evt.keyCode == keys.DELETE && evt.ctrlKey) {
                        this._clearValue();
                    }
                });
                dojo.place(this.clearNode, this.domNode);
            },

            _clearValue: function() {
                this.set("value", null);
            },

            _setReadOnlyAttr: function(readOnly) {
                this.inherited(arguments);
                if (this.clearNode != null) {
                    domStyle.set(this.clearNode, "display", "none");
                }
                domStyle.set(this.clearNode, "display", readOnly ? "none" : "block");
            }
        });
    });

Editor descriptor

using System;
using EPiServer.Shell.ObjectEditing.EditorDescriptors;

namespace EpiServerThumbnail.Business.EditorDescriptors
{
    [EditorDescriptorRegistration(TargetType = typeof(DateTime?), UIHint = UIHint)]
    public class NullableDateEditorDescriptor : DateTimeEditorDescriptor
    {
        public const string UIHint = "nullable-date";

        public NullableDateEditorDescriptor()
        {
            this.ClientEditingClass = "alloy.editors.nullableDateTimeSelectorDropDown";
        }
    }
}

Uning in model

[Display(Name="Nullable date", GroupName = SystemTabNames.Content, Order = 340)]
[UIHint(NullableDateEditorDescriptor.UIHint)]
public virtual DateTime? NullableDate { get; set; }