Hi. Premium user - how can I see when a task was completed?
In other upper right corner of the screen, you should see an icon for the productivity trend/karma trend (it's the one that's red).
Click this and it should give a couple of information. One of which is if the completed history. Click "View All Completed" and filter it as needed (by date, by project, by label).
This should show you when a task was completed and what time.