# startOf()

Returns a date that is the start of a unit of time for the given date.

## Signature

`startOf(string | number | Date date, string unit)`

## Parameters

***date*:** Type: `string | number | Date`. A datetime string in ISO8601 format, or a timestamp in milliseconds, or a `Date` object.

***unit*:** Type: `string`. A datetime unit. Options are 'year', 'month', 'week', 'day', 'hour', 'minute', or 'second'.

## Returns

**Type: `Date`** A JavaScript `Date` object. If a unit is not provided, returns a parsed date.

## Sample Code

```javascript
var date = "2015-10-9";
// Returns "Thu Oct 01 2015 00:00:00 GMT-0700 (PDT)"
$A.localizationService.startOf(date, 'month');
```