Hi,
Change FY Variant is a very complicative process.
Please Read OSS notes:
210861 Changing fiscal year variant in production system
193713 SAPF070: Change of fiscal year variant
672255 Set up shortened fiscal year / change fiscal year
202687 OB29: FGV(600) / FGV(602) in fiscal year variant ma
173636 OB29: Maintnce fiscal year variants FGV572, FGV610
http://help.sap.com/saphelp_46c/helpdata/en/4f/71eae3448011d189f00000e81ddfac/content.htm
Fiscal year change was discussed in detail in the below SCN Thread.
http://scn.sap.com/thread/1883475
Regards,