# week_first_day({date})

Accepts a `DateTime`, `DateOnly`, or legacy Date object as input. Returns an object of the same type that corresponds to the first day (Sunday) of the week that contains the specified date.

## Example

```nolang
SELECT OrderDate as "date", week_first_day(OrderDate) as "week_first_day" FROM "dates_sample_data";
```

| date                | week_first_day      |
| ------------------- | ------------------- |
| 2015-01-21 15:30:00 | 2015-01-18 00:00:00 |
| 2015-01-21 00:00:00 | 2015-01-18 00:00:00 |
| 2015-01-31 10:00:30 | 2015-01-25 00:00:00 |
| 2015-02-03 15:30:00 | 2015-02-01 00:00:00 |
| 2016-01-21 23:59:59 | 2016-01-17 00:00:00 |
| 2015-10-31 23:59:59 | 2015-10-25 00:00:00 |
| 2015-12-03 00:00:00 | 2015-11-29 00:00:00 |
| 2016-01-11 03:30:00 | 2016-01-10 00:00:00 |
| 2016-01-11 03:30:00 | 2016-01-10 00:00:00 |