> For the complete documentation index, see [llms.txt](https://docs.wem.io/platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wem.io/platform/wemreference/functions/date/datediff.md).

# DateDiff

{% hint style="info" %}
The **`DateDiff()`** function calculates the difference between two dates. You can use the DateDiff for the difference in: year, month, week, day, hour, minute or second. 

This function is NOT SQL compatible. For more information about SQL compatibility, see our [documentation](/platform/wemreference/sql-compatibility.md).
{% endhint %}

{% hint style="success" %}
Returns a <mark style="color:green;">number</mark> that is the difference between two dates in a specific unit. If one of the two dates is unknown then this function returns unknown.

Returns <mark style="color:red;">**`Unknown`**</mark> if one of the parameter values is unknown or outside the common valid date boundaries.
{% endhint %}

### Syntax

<details>

<summary><code>DateDiff(</code><mark style="color:blue;"><code>start_date</code></mark><code>, </code><mark style="color:blue;"><code>end_date</code></mark><code>, </code><mark style="color:blue;"><code>unit</code></mark><code>)</code></summary>

`DateDiff('2014-08-21', '2002-12-31', Year)`\
\=>*Result: 11*

`DateDiff()`\
\=>*Result: unknown*

</details>

### Parameters

<table><thead><tr><th width="150">Name</th><th width="150">Type</th><th width="150" align="center">Required</th><th width="248.15953250810662">Description</th><th data-hidden>Required?</th></tr></thead><tbody><tr><td><mark style="color:blue;"><code>start_date</code></mark></td><td>date time</td><td align="center"><span data-gb-custom-inline data-tag="emoji" data-code="2611">☑️</span></td><td>the start date</td><td>yes</td></tr><tr><td><mark style="color:blue;"><code>end_date</code></mark></td><td>date time</td><td align="center"><span data-gb-custom-inline data-tag="emoji" data-code="2611">☑️</span></td><td>the end date</td><td>yes</td></tr><tr><td><mark style="color:blue;"><code>unit</code></mark></td><td>Keyword</td><td align="center"><span data-gb-custom-inline data-tag="emoji" data-code="2611">☑️</span></td><td>the date unit of which the difference is calculated.<br>Possible values: years, months, weeks, day, hour, minute or second.</td><td>yes</td></tr></tbody></table>


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