It'll determine when you're asleep, characterized by a lower heart rate, and when you've exercised, generally characterized by a higher heart rate (unless, of course, you're exceptionally fit). That's where Garmin's new Lifestyle Logging feature comes in. You don't need a specific watch to use the Lifestyle Logging feature, as it's widely available in the Garmin Connect app. Just make sure you've updated Garmin Connect, and you should be able to find the feature under More > Health Stats > Lifestyle Logging. Navigate to the Lifestyle Logging tab during the day to log or edit behaviors.