What is the best "Actual finish date" of a shop order operation?

I want to know the date when an operation is actually finished, not planned to be finished.

What I find to be most accurate was the latest entry of the Date applied below.

Created a custom field on Shop_order_operations_CFV that works but it is too slow.

select Date_applied from OPER_AND_IND_HIST_UIV HIST, SHOP_ORDER_OPERATION_JOIN SOOJ
where HIST.Order_no=SOOJ.ORDER_NO--'13870'
and HIST.Operation_no=SOOJ.operation_no--'20'
And HIST.Release_no=SOOJ.release_no--'*'
And HIST.Sequence_no =SOOJ.Release_no--'*'
And SOOJ.objkey=:objkey
Order by Date_applied desc
Fetch First 1 rows only

Works, but it is to slow to be used in many applications.

Is there any available function or field I do not know about?

@Björn Hultgren, you seem to know your way around these areas?