Period adapted to posting date

What causes this issue?

You changed an entry in the field <LS>Posting date</> or the field
<LS>Period</> so that the posting date is no longer in the period. This
is only permitted if the posting date is in the last period of the
fiscal year and the period specified is a special period.

System Response

The system entered in the field <LS>Period</> the period in which the
posting date falls.

Error message extract from SAP system. Copyright SAP SE.