We need to set up two date/time custom fields for the Calendar. Add-on uses them to show issues in views. For example, you can create the following custom fields:

"Start Date" and "Finish Date".

Adding these fields to the screens is not necessary.

The field types should be Date Picker if you have whole-day issues only and Date Time Picker if you need issues to start and finish at the precise time.

After creating the fields you need:

• go to JIRAAdministration menu \ Add-ons \ Calendar;
• specify the fields. If the "Start Date" is of type "Date", 
• "End Date" must also be of the same type: