Joi.array() modifies original array

I'm validating an array of times with

``` js
var schedule = [
    '08:00',
    '16:00'
];

var result = Joi.validate({
    schedule: schedule
}, {
    schedule: Joi.array().includes(Joi.date().format('HH:mm')).unique().required()
});
```

After the validation `schedule` becomes an array of dates when I expect only `result.value.schedule` to be an array of casted values.
