A Calendar and Year window exists in iDempiere to define the specific calendar that will be used for reporting and period control.  This is specially useful before new entries are made at the start of the calendar month.  When a calendar doesn’t exist or a period is closed (ex. transitioning from Dec 2019 to Jan 2020 to a 2020 calendar that doesn’t exist and/or a Jan period that is closed), transactions will not be completed. It will return an error of “Period Closed…”.

The solution to this issue is simple.  First, check if the calendar exists (via the Calendar and Year window). If it doesn’t, you will need to create a new calendar and create all the periods within the calendar.   Secondly, make sure that the month (i.e. period) that you will be working on is open. A “Period Closed…” error will not occur if a calendar exists and the specific period is open.

Related to the calendar is the concept of history and future days.  In the Accounting schema window, you can specify the number of previous days from the current date (i.e history) and the number of advance days from the current date (i.e. future days) a transaction can be done.