If we specify a past date in the "Need By Date" field in a Change Order or an Issue and attempt to save it, the following error appears and the save does not complete.
Error 1 attempting to set need_by to "xxxxxx": AHD05728:This date cannot be before the Actual Start date.
This is working by design.
The date validation is set so that the "Need By Date" field cannot contain a past date. There is no setting to disable this check.
If you would like to set the past date on the ticket, a customization would be required. For example: You could create a create a new date field that allows you to input a past date value.