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

# week_start_day - Dimensions

> Defines the day that weeks start on for a specific dimension.

Defines the day that weeks start on for a specific dimension. This parameter can only be added to a dimension and should only be used on date, time, or timestamp dimensions.

<Note>
  `week_start_day` can also be set at the [model](/modeling/models/week-start-day) and [topic levels](/modeling/topics/parameters/week-start-day). When set at more than one level, the most specific setting is applied: dimension overrides topic, and topic overrides model.
</Note>

## Syntax

```yaml theme={null}
<dimension_name>:
  week_start_day: <day_of_week>
```

## Properties

<ParamField path="dimension_name" type="object">
  The name of the dimension. Dimension names must:

  * Be unique within the view
  * Start with a letter
  * Contain only alphanumeric characters and underscores

  <Expandable title="dimension_name properties" defaultOpen="true">
    <ParamField path="week_start_day" type="string">
      The day of the week that weeks start on for this dimension. Valid values are: `Monday`, `Tuesday`, `Wednesday`, `Thursday`, `Friday`, `Saturday`, `Sunday`.

      Unlike the model-level and topic-level settings, this value must be a plain day name. User attributes aren't supported for this parameter.
    </ParamField>
  </Expandable>
</ParamField>

## Examples

```yaml title="Set week start day on a dimension" theme={null}
shipped_at:
  sql: shipped_at
  week_start_day: Thursday
```