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title: atBeginningOfDay
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release: "2.12"
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---
---
product: DataWeave
version: 2.12
---

# atBeginningOfDay

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

## atBeginningOfDay(dateTime: DateTime): DateTime

Returns a new `DateTime` value that changes the `Time` value in the input to the beginning of the
specified _day_.

The hours, minutes, and seconds in the input change to `00:00:00`.

_Introduced in DataWeave version 2.4.0._

### Parameters

<table><colgroup><col> <col></colgroup><thead><tr><th>Name</th><th>Description</th></tr></thead><tbody><tr><td><p><code>dateTime</code></p></td><td><div><div><p>The <code>DateTime</code> value to reference.</p></div></div></td></tr></tbody></table>

### Example

This example changes the `Time` value within the `DateTime` input to the beginning of the specified
day.

#### Source

```DataWeave
%dw 2.0
import * from dw::core::Dates
output application/json
---
{
  "atBeginningOfDayDateTime": atBeginningOfDay(|2020-10-06T18:23:20.351-03:00|)
}
```

#### Output

```Json
{
  "atBeginningOfDayDateTime": "2020-10-06T00:00:00-03:00"
}
```

## atBeginningOfDay(localDateTime: LocalDateTime): LocalDateTime

Returns a new `LocalDateTime` value that changes the `Time` value within the input to the start of
the specified _day_.

The hours, minutes, and seconds in the input change to `00:00:00`.

_Introduced in DataWeave version 2.4.0._

### Parameters

<table><colgroup><col> <col></colgroup><thead><tr><th>Name</th><th>Description</th></tr></thead><tbody><tr><td><p><code>localDateTime</code></p></td><td><div><div><p>The <code>LocalDateTime</code> value to reference.</p></div></div></td></tr></tbody></table>

### Example

This example changes the `Time` value within the `LocalDateTime` input to the beginning of the
specified day.

#### Source

```DataWeave
%dw 2.0
import * from dw::core::Dates
output application/json
---
{
  "atBeginningOfDayLocalDateTime": atBeginningOfDay(|2020-10-06T18:23:20.351|)
}
```

#### Output

```Json
{
  "atBeginningOfDayLocalDateTime": "2020-10-06T00:00:00"
}
```