I have a date field in a table named product. I need to add some days to this field how to d this. I am new to PostgreSQL.

I tried this:

```
select manufacture_dt + weeks*7 from product;

```

It is giving me the error

```none
operator does not exist: timestamp without time zone + integer.
Hint no operator matches the given name and argument types .you might need to add  explicit type cast

```