Solution : https://service.sap.com/sap/support/notes/1539300 (SAP Service marketplace login required)
Key words : 
fiscal year variant occur, fiscal year variant, shortened fiscal year, bw data target, usual 12+ special periods, aied delta mode, usual subsequent periods, delta process add, correct subsequent period, ec-pca extraction
Related Notes : 
       
| 672255 | Shortened fiscal year/changing fiscal periods |