One of the most important attributes to keep a project up to date are the plan start, plan end, actual start, actual end.
Between plan and actual, the difference is that when you create your project schedule, it's not possible to know exactly when the cards are going to happen (actual), only make estimates (plan).
That's why the actual start date will be only visible when the status is set to at least started, so you know for a fact the date when the card started. The same logic applies to the actual end date, that can be filled only when the status is set to completed.
Also, it is required to click Show empty attributes on the right panel to view those dates.