One way of determining if a period has been closed is to look in the general journal file to see if there is a closing entry for the period.
The following screen shows the closing entry for period 1 in 1983.
The debit entries close out the revenue accounts (7000s), and the credit entries close out the expense accounts (6000s). The difference between the total for the revenue accounts and the total for the expense accounts is credited to the retained earnings account (3200).
Notice that the date of the general journal entry is the first day of the next period. This is done so the Income Statement and Balance Sheet report will show the correct amounts for the revenue and expense accounts for the period. If the closing entries were dated the last day of the period, the balances for the expense and revenue accounts would show up as zero on the Income Statement.