disabledStartDate = (current) = > {
const endValue = this.state.endValue;
// if (!startValue || !endValue) {
//   return false;
// }
// return  startValue.valueOf() > endValue.valueOf();
return current < moment();} 
 disabledDate= {this.disabledStartDate} 
 set a date that is not selectable in disabledDate, and how can you make that day an optional  
 
