In Microsoft Dynamics NAV, if you are in a Firm Planned Production Order and you select ‘Refresh Production Order’ from the Home tab of the ribbon,
and you get an error like this, saying “Error when calculating backward. Calendar is not available before…. for Work Center ….”
Go to the Work Center card and check to see if you have a Work Center where ‘Consolidated Calendars’ in the Scheduling tab is set to yes (this flag should only be set to Yes if he Work Center has Machine Centers assigned to it)
Go to the Work Center List and select ‘Calculate Work Center Calendar’, and enter a date range.
Filter on the ‘Work Center’ tab on the ‘No.’ of the Work Center, and select OK.
Select the Home tab and then select ‘Load’
You should now see capacity.
Go ahead and ‘Refresh Production Order’ again and it should now continue without an error.