This is where historical periods are displayed. Each year shown has history posted in it. The first time a user clicks this tab they are able to define historical periods. It defaults to the same as the current fiscal periods, but if a company has previously changed their year-end, they can edit this tab to match history. Once set and accepted it can take some time to save.
This must be defined before the first Year End is processed, if you have imported data from another accounting system.
Once the user clicks ‘Save’ they get this message and clicking Yes saves the historical periods and cannot be edited again.