> ## Documentation Index
> Fetch the complete documentation index at: https://help.dingtalk.io/llms.txt
> Use this file to discover all available pages before exploring further.

# ISOWEEKNUM

> The ISOWEEKNUM function calculates the ISO week number of a specified date based on the ISO 8601 standard, and can be used in various YiDA scenarios such as Form and workflow design.

The **ISOWEEKNUM** function is used to get the ISO week number of a specified date. The ISO week number determines the position of a week within a year according to the ISO 8601 standard.

ISO 8601 specifies that each week starts on Monday, and the first week of each year is the week containing the first Thursday of the Gregorian year.

## Supported Product Scenarios

The ISOWEEKNUM function can be used in the following YiDA scenarios.

* Form (main table Field)
* Form (business Association rule)
* Form (validation)
* workflow design (validation rule)
* workflow design (Association Action)
* integration & automation
* Workflow node
* Connector

## Format

```text theme={"theme":{"light":"github-light","dark":"github-dark"}}
ISOWEEKNUM(date)
```

## Attribute Description

| **Attribute** | **Required** | **Description** |
| ------------- | ------------ | --------------- |
| date          | Yes          | Time object.    |

## Back Value

| **Back value Type** | **Description**                          |
| ------------------- | ---------------------------------------- |
| Number              | Returns the ISO week number of the date. |

## Usage Example

As shown in the figure below, you can use the `ISOWEEKNUM()` function to get the week number of a specified date.

## Try It Out

Returns the week number of a specified date within the current year.