> For the complete documentation index, see [llms.txt](https://developer.collibra.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.collibra.com/tutorials/working-with-date-attributes.md).

# Working with date attributes

The Collibra Platform uses [Unix timestamps](https://en.wikipedia.org/wiki/Unix_time) in milliseconds to store dates and time.

{% tabs %}
{% tab title="Example" icon="glasses-round" %}
December 30, 2021 is `1640822400000` in Unix timestamp in milliseconds
{% endtab %}
{% endtabs %}

When you interact with the Collibra Platform through an API, use the Unix timestamp in milliseconds to specify a date. In most cases, the date must be in UTC at midnight: hours, minutes, seconds and milliseconds set to `0`.

{% hint style="success" %}
Use [EpochConverter](https://www.epochconverter.com) to convert to and from Unix timestamps and find conversion code snippets.
{% endhint %}

An example where a timestamp is required is updating the expiration date of an asset through the Core REST API v2. The following call sets the value of an expiration date attribute to June 30, 2020.

```
curl -X PATCH \
	https://<your_dgc_environment_url>/rest/2.0/attributes/<your_attribute_uuid> \
	-H 'Content-Type: application/json' \
	-d '{
	"value": "1593475200000"
}'

```

{% hint style="info" %}
Values that do not represent a UTC time at midnight are invalid and trigger a "Value not allowed" error.
{% endhint %}

In some cases, the API allows variations, for example, as of Collibra 5.7, the REST Import API v2 and Collibra Connect also support ISO 8601 dates in UTC at midnight for date attributes.


---

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