Solution : https://service.sap.com/sap/support/notes/997710 (SAP Service marketplace login required)
Key words : 
terms variant dynamic date calculation start date end date selection option reason, dynamic requirement date calculation separately, requirement date selection option, end date belong, start date, transaction /sapapo/md74, selection screen, separated fields, solution write, development request
Related Notes : 
       
| 1413551 | Implementation recommendations for SCM 4.1 | 
| 1413544 | Implementation recommendations for SCM 5.0 | 
| 832393 | Release Restrictions for SCM 5.0 | 
| 713429 | Release Restrictions for SCM 4.1 |