Solution : https://service.sap.com/sap/support/notes/625171 (SAP Service marketplace login required)
Key words : 
subactivity solution implement, symptom dates, external system, terms stv_tex, program correction, subactivity, scheduling
Related Notes : 
       
| 634869 | SAPKU40001: Support Package 01 for CRM 4.0 | 
| 628033 | RI: Dates for activity element not correctly transferred | 
| 607000 | Required notes for PS-BAPIs |