The nest system can notice when you at home or away from home using sensors and learning algorithms. You can also set it manually on the nest learning thermostat or via the nest app. When Hue nest sees that you've moved away from home it will take care to slowly fade of all the hue lights in your home. If you've been away for more than 24 hours, it will also enable schedules in the bridge to simulate your presence. Once you come home again these schedules will be disabled. The burglar deterrent schedule turns on the lights between 7 and 9am and then again between 6 and 11pm, with a bit of randomness to make it seem natural.