The Act. End Date is the actual operation end date set by the system when the operation is reported complete. The “Date Worked” in Job Status Updating is used to assign this value.  In operation grid displays an "(R)" will appear next to the title to show you that it is a read only field.

If displaying the actual operation end date at the job header level, the term will appear as "Act. Op. End" and shows the latest actual operation end date for the job.