# Date.format

## Function

Output date and time in chrono/strftime style format string.

## Syntax

```bt
date_value.format(pattern)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| pattern | String | No | `%Y-%m-%d %H:%M:%S` | Format string. |

## Return value

| Type | Description |
| ------ | ------ |
| String | Returns the formatted date string. |

## Code Example

```bt
d = date('2026-06-09 10:11:12')

result = d.format('%Y-%m-%d')

// Output: 2026-06-09
```

## Notes

- Format characters use chrono/strftime style, such as `%Y-%m-%d %H:%M:%S`, `%F %T`.
- When pattern is not passed, `%Y-%m-%d %H:%M:%S` format is returned.