You can update your user's individual business hours from the View User pop-up window. First, click on the Pencil icon:
You will then be redirected to the Settings for User page; on this page uncheck the "Use Global Settings" option:
Then click on the Save button to go back to the user profile.
Once you are back on the "Settings" tab, there will now be a Plus Sign icon in the "Business Hours" panel; click on the Plus Sign icon:
The Add Business Hours pop-up window will then appear:
From this pop-up window you can input the following data:
The days of the week the user will be available.
The start time that the user begins their day.
And the end time that the user ends their day.
Once you are satisfied with the information entered, click the Save button to confirm the user's schedule.