react-dateTime picker Css not working

I am using react-dateTime Picker. react-datetime picker's css is not working.can any one tell me why it look like. It looks like this.

and second one this following function is working but css is working.

var yesterday = Datetime.moment().subtract( 1, 'day' );
var valid = function( current ){
    return current.isAfter( yesterday );
};