ISY-99i/ISY-26 INSTEON:Configuring Physical Location
The ISY has the capability to calculate the sunrise or sunset time based on the physical location set in the device. By using the Sunrise or Sunset time to control the light, this ensures that lights are efficiently turned on at dusk and/or turn off at dawn.
To set or change the location of the ISY, select the Change Location button. For a relatively accurate Sunrise/Sunset calculations, select the closest city in which the ISY will be physically located. If the city you are located in does not appear on the list select the closest city with the same time zone.
It is also possible to enter the exact coordinates of your location by selecting Custom Location. Microsoft Research Maps is a site that will allow you to find the latitude and longitude of a city or even a specific address.