Adjusting period is just another period. There is nothing special about it other than it spans only one day (usually 31-DEC which could overlap other period).
Lets say you have two periods: period 1 and period 2.
If you enter and post a journal in period 1, the PTD balances in period 1 will be affected (for the accounts used in the journal). PTD (period to date) balances of period 2 will not be changed.
However, YTD (year to date) balances for period 1 and all subsequent periods (including period 2) will be affected.
If you enter and post a journal in period 2, the PTD balances in period 2 will be affected (for the accounts used in the journal). PTD (period to date) balances of period 1 will not be changed.
Also the YTD (year to date) balances for period 2 and all subsequent periods will be affected. YTD balances of period 1 will not be changed. Hope this helps.