Navigate to the settings tab on the service desk module. You will see a new area called Service Desk with a button for Business Hours.
Here you can set when your service desk is open which will have an impact on your First Resolution Target, Update Target and Resolution Target.
You are also able to add new business hours or edit/delete existing ones if required. You can set the service desk to be open 24 hours.
Any changes made in this area can be seen in the history logs tab as shown below:
This will allow you to see who made the changes in this area and when.
Please note that if the issue type is classed as emergency works, the issue targets will not be restricted to the hours set in this area.