What version/SP of BI4 are you using?
According to this document http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/302cb4a7-226d-3010-0099-9555032fc635?overridelayout=t…
time dependent hierarchies are supported with BI4 SP5
If you are on that version or higher and getting this error I recommend creating an incident with SAP Support
