Organizational Unit: Validity Dates 
Use
You create organizational units (OU) with a specific validity. . You cannot use an OU outside of this validity period. In other words, you cannot assign movements or other OUs within the organizational structure to OUs outside of their specified validity periods.

If you want to transfer legacy data from a previous system, you have to set the validity start date of the OUs in such a way that the OUs are valid when the movements of the transferred cases take place.
If you want to shut down an OU, you should delimit the validity of the OU accordingly and set the blocking indicator.
Activities
You enter the validity dates on the Description tab page.