Planning of special periods is not supported

What causes this issue?

The planning parameters entered on the initial screen contain a
planning period (&V1& - &V2&) which contains special periods defined in
fiscal year variant &V3&.
However, you cannot plan special periods.
The number of actual periods for this variant is &V4&.

System Response

The controlling area and planning parameters you entered cannot be used
together.

How to fix this error?

Check your entries.

Error message extract from SAP system. Copyright SAP SE.