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

# Duration

> Set when the experiment starts, how it stops, and who gets notified when it finishes.

Duration controls the experiment's running window. Set a start date, and either an end date or nothing at all — an experiment with no end date runs until you end it manually.

## Configuration Details

<Frame>
  <img src="https://mintcdn.com/experro/H32RAWpqB_urQLNk/images/experiments/a_b_testing/ab_duration.png?fit=max&auto=format&n=H32RAWpqB_urQLNk&q=85&s=2f9072057d3c1292ec37fcac4a7cc4a6" alt="" width="1917" height="917" data-path="images/experiments/a_b_testing/ab_duration.png" />
</Frame>

| Field                  | Required | Description                                                 |
| ---------------------- | -------- | ----------------------------------------------------------- |
| **Start Date**         | Yes      | When the experiment begins. A future date schedules it.     |
| **End Date**           | No       | When the experiment stops. Leave empty to run indefinitely. |
| **Email Notification** | No       | Addresses to notify when the experiment completes.          |

## Email Notification

Start typing a name or address and Experro suggests matching users. To notify someone outside the workspace, type the full address and press **Enter**.

You can add as many recipients as you need. Badly formatted addresses are rejected with an inline message.

## Key Considerations

* **Start Date** and **End Date** are a single linked range. The end date must fall after the start date.
* If no end date is set, the experiment runs until you end it manually. Results show `∞ days` in place of a countdown.
* A draft whose end date has already passed cannot be started until you move the date forward.

<Warning>
  Leave a gap of more than three minutes between the start and end dates. The scheduler runs every three minutes, and a shorter window may never publish.
</Warning>

## What's Next

* [Variants](/experiments/a_b_testing/variants)