What is a Period Calculation Basis?

The period calculation basisClosed Defines the interval between end dates when you split a financial year into periods defines the interval between end dates when you split a financial year into periods.

The options are:

Month Specifies that the start of a period will fall on the same date of each month. If the 31, 30 or 29 is selected, the period start for those months which do not contain the date will fall on the first day of the following month.
Month End Specifies that the end of a period will fall on the last day of the month. For example, consecutive periods would end on the 30 September and 31 October.
445 Specifies that period-ends in a quarter will occur every 4, 4, and 5 weeks. The cycle repeats for the next quarter.
454 Specifies that period-ends in a quarter will occur every 4, 5, and 4 weeks. The cycle repeats for the next quarter.
544 Specifies that period-ends in a quarter will occur every 5, 4, and 4 weeks. The cycle repeats for the next quarter.
Custom Indicates that the period details have been customized (edited) after period generation.

You specify the number of accounting periods for a company and its period calculation basis in the Year object.