allow empty default date value

docs/widgets.md

@@ -99,3 +99,14 @@ collections:
         searchFields: [name, twitterHandle]
         valueField: name
 ```
+
+### Date Widget / DateTime Widget
+
+The date and datetime widgets provide date or datetime pickers when the widget is active. The resulting date string can be formatted (uses Moment.js), and accepts a default value. The initial value will be the current date unless `false` or an empty string are provided as the default value.
+
+The following field configuration properties are specific to fields using the date or datetime widget:
+
+Property | Accepted Values | Description
+--- | --- | ---
+`format` | string | format string uses Moment.js [tokens](https://momentjs.com/docs/#/parsing/string-format/)
+`default` | boolean, string | can be a date string, or else an empty string - defaults to current date

src/components/Widgets/DateControl.js

@@ -7,7 +7,12 @@ export default class DateControl extends React.Component {
   componentDidMount() {
     const { value, field, onChange } = this.props;
     this.format = field.get('format');
-    if (!value) {
+
+    /**
+     * Set the current date as default value if no default value is provided. An
+     * empty string means the value is intentionally blank.
+     */
+    if (!value && value !== '') {
       this.handleChange(new Date());
     }
   }
@@ -16,7 +21,7 @@ export default class DateControl extends React.Component {
     const newValue = this.format
       ? moment(datetime).format(this.format)
       : datetime;
-    onChange(newValue);
+    this.props.onChange(newValue);
   };
 
   render() {