I am developing report under customer report of opportunity.

I found I can add "fiscal period" field to report layout by using report builder tool, when I selected existed report type such as opportunity->opportunity.

But I can find "fiscal period" field, when I selected custom report type which created by myself.

I known, "fiscal period" field is hidden field of opportunity. But how can I add it to my custom report type. Or my requirements is can't be implement in custom report type.