Hi,
You can manually change the depreciation start date in Asset Master > Depreciation Area > Depreciation Start Date. After this change, run AFAR and then AFAB to recalculate depreciation.
However, depreciation will be recalculated only for the fiscal years that are open in Asset Accounting (OAAQ and OAAR). If the changed depreciation start date is before the open fiscal years, then depreciation recalculation is limited to the open fiscal years.
Regards,
Ravi Kumar