When using your boards as Kanbans, it can be useful to enable Lead time. This allows you to track how long it takes for a card to travel through the length of the board. You enable this from the App Store in the hamburger menu of your board.
Once enabled, you will see a time stamp on your cards which can help you when working on velocity and trying to find bottlenecks in your workflow. The time will keep ticking away until the card reaches the right-most column.
Each user has the opportunity to show/hide lead times on cards through the Show lead time on cards options.