title: How to edit time in react material ui KeyboardDatePicker if time as string?
body: <p>I already follow the docs that works well with date object for pickup time and edit time but problem arise when i have custom time that stored in database like 04:00 PM and on edit event i have to display that time on textfield and edit but edit can't works because format is 
  timestring.</p>
  
  <p>docs: <a href="https://material-ui-pickers.dev" rel="nofollow noreferrer">https://material-ui-pickers.dev</a></p>
  
  <p><a href="https://codesandbox.io/s/lucid-varahamihira-2unp9" rel="nofollow noreferrer">https://codesandbox.io/s/lucid-varahamihira-2unp9</a></p>
  
  <p>Here the relevant code :</p>
  
  <pre><code>handleStartTimeChange(date) {
      this.setState({
        offerStartTime: date
      });
    }
    editTime() {
      this.setState({
        custom_time: "03:00 PM"
      });
    }
    render() {
      return (
        &lt;div className="app"&gt;
          &lt;Timepicker
            value={this.state.offerStartTime}
            onChange={date =&gt; this.handleStartTimeChange(date)}
            inputValue={this.state.custom_time}
          /&gt;
          &lt;button onClick={() =&gt; this.editTime()} style={{ marginTop: "0px" }}&gt;
            Edit
          &lt;/button&gt;
        &lt;/div&gt;
      );
    }
  </code></pre>