SAP Message RTCMMD124 - Validity change only for full delivery periods, as OTB change involved

Diagnosis
An OTB relevant change was made. The reference date for determining thetime-dependent master data and structure data is always the deliverydate of the respective OTB-relevant purchasing document item.
The time-dependent attributes and material hierarchy assignment cannotchange within a delivery period.

System Response
The system automatically adjusts the reference date to the OTB deliverydate.