This tab appears in many dialogs (for example the Account card) and can specify the period to be show or to be calculated.
If for example a quarter is selected: in the account card only the transactions of the selected quarter will be shown, and in the balance sheet only the results for the selected quarter will be calculated.
If this option is selected, the entire accounting period is included.
If a specified period is desired, indicate the start and end dates.
Transactions with no date
If there are transactions with no date, they will be considered only if you chose the whole period (All...)
If however you enter the initial and final dates January 1sr and December 31, the transactions with no date will not be included in the report.