Due to the limited screen space, the Apple Watch adds timestamps to your messaging conversations far less frequently, so it may not be clear just by glancing when a given message was actually sent or received. Fortunately there’s an easy way to check this out, and it works the same way as it does on your iPhone.
When viewing the message list, pull any conversation bubble to the left and you’ll see the timestamps displayed beside each message indicating when it was sent from your Apple Watch or received by it. You can still scroll up and down through the conversation, and releasing your finger will pop back to the normal view.