Using refs for components. I have not tested other components but it seems using refs on for example Input component does not work and the input is not made available. If I replace this with a regular input then everything works as expected.

https://facebook.github.io/react/docs/more-about-refs.html

I used the input like this:

<Input
  ref={ (ref) => this._input = ref }
  { ...input }
  type="text"
  onChange={ this.handleInputChange }
  onFocus={ this.handleInputFocus }
  onBlur={ this.handleInputBlur }
/>

With the datepicker overylay example from here:
http://react-day-picker.js.org/examples/?overlay