In Data Management Period Mapping, we don't have option to update bulk periods at a time. We have export option to export to excel but do not have option to import. Manually we have to update each period.
But we can do bulk update using Migration option in EPBCS, may be in On-premise also. I do not have On-premise environment to check that. So, steps to update in EPBCS as follows:
Go to Tools à Migration
Click on Data Management in the listIn Artifacts list, Select Global Setup Artifacts, Uncheck and select Period Mapping only.
Before this step, Try to add at least 2 periods in the list.
Click on Export to complete the migration.
Use EOMONTH(date,0) function to get last date of each month. Drag the list up to year which we have in the application. we can prepare sheet in excel easily.