Search for date in filter

I'm using ngbDatepicker, which means it stores date on the database as an object, such as:

`{year: 2018, month: 8, day: 18}`

I can't use the built-in filter on it.

So I added an external filter with an ngbDatepicker input, and when I select the value I'm using this code:

```
onSearch() {
console.log(this.dateModel);
this.source.setFilter([
// fields we want to include in the search
{
field: 'expirationDate',
search: this.dateModel
}
], false);
}
```

Does it work? No.

How can I search for date when date is an object?