Solution : https://service.sap.com/sap/support/notes/609214 (SAP Service marketplace login required)
Key words :
EPS, BAPI, duration, start date, end date, BAPI_PROJECT_MAINTAIN
Related Notes :
| 634869 | SAPKU40001: Support Package 01 for CRM 4.0 |
| 608790 | BAPIs:Specifying dates and duration simultaneously |