A sandbox automatically ends when it's end date is reached. You can update the duration of the sandbox before it reached its end time.  

Extending a Sandbox

To extend the duration of a sandbox: 

1. Open the required sandbox. 
2. In the top tool bar, on the right, click 
3. Define the amount of time to be added to the duration of your sandbox.
4. Click Update.  

Ending a Sandbox 

To end a Sandbox: 

1. Open the required sandbox. 
2. In the top tool bar, on the right, click  and confirm the action. 

NOTE: When a sandbox ends, all relevant cloud resources are permanently deleted.