Answer:
The following steps should be followed to create the calculated field:
1. Enter AccountTime: (The AccountTime must be enclosed in #). #12/31/2017#-OpenDate in the first empty field.
2. Right-click the field then click properties. This will allow you format the selected field.
3. Rght-click the query tab and click Save. This will allow you save the query
4. Lastly, Close the query.