To change the Accounts period you need to close the account first.
1. Go to Accounts section and close the account

2. Go to Edit Master > Edit Account list

3. Select the account and click on Edit.

4. Go to second tab and change the year.
1. Go to Accounts section and close the account
2. Go to Edit Master > Edit Account list
3. Select the account and click on Edit.
4. Go to second tab and change the year.