If you look at a text message thread, you normally only see the messages back and forth without knowing exact when a message was sent or received.
Now with iOS 7, you can reveal the timestamp for every single message you have sent or received in a thread. Just swipe one of the speech bubbles to the left, and see what happened. Note that, the timestamps disappear once you release your finger from the screen.
Never excuse, never argue about exactly when the message was sent because, seriously, I have the proof right in front of your eyes.