LiveDate.jsx

class LiveDate extends React.Component {
  componentDidMount() {
    // update state every second with
    // the current time    
    setInterval(() => {
      this.setState({
        liveDate: new Date().toISOString(),
      });
    }, 1000);
  }

  render () {
    return this.props.children({
      date: this.state.liveDate || "loading..."
    });
  }
}