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> Extract day as days from 1970-01-01 according to Iceberg partition transforms

# ICEBERG_DAY

Extracts the day from a date or timestamp value and returns it as the number of days since 1970-01-01, according to the [Iceberg partition transforms specification](https://iceberg.apache.org/spec/#partition-transforms).

## Syntax

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
ICEBERG_DAY(<value>)
```

## Parameters

| Parameter | Description                                          | Supported input types              |
| :-------- | :--------------------------------------------------- | :--------------------------------- |
| `<value>` | The date or timestamp value to extract the day from. | `DATE`, `TIMESTAMP`, `TIMESTAMPTZ` |

## Return type

`INTEGER`

Returns the number of days since 1970-01-01. For dates before 1970-01-01, returns a negative value.

## Remarks

The `ICEBERG_DAY` function can be used in the `PARTITION BY` clause of [`CREATE ICEBERG TABLE`](/reference-sql/commands/data-definition/create-iceberg-table-as-select) commands.

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
CREATE ICEBERG TABLE events
  PARTITION BY (iceberg_day(event_date))
  AS SELECT * FROM source_events
WITH LOCATION = my_iceberg_location;
```

## Example

```sql theme={"theme":{"light":"github-light","dark":"github-dark"}}
SELECT iceberg_day('2025-12-15'::DATE) AS day_partition;
```

**Returns:**

| day\_partition |
| :------------- |
| 20437          |