How to apply 50% bonus depreciation method for previous year closed period

As per new IRS law, we want to apply  50% Bonus Depreciation Methods for assets in dec-15 but unfortunately that period is closed.how can we pass adjustment entry in previous period if it is closed.

or if we change the depreciation method now , will FA calculate the catchup depreciation and apply in dec-15 or it will apply in jan-15.

is there any way to make the catchup depreciation applied to dec-15.

thanks