By default Iris will detect your location automatically, but if for some reason it detects it wrong you can set Manual location or night duration from here.
Common reason for wrong detection is no internet connection, VPN or strange proxy configurations.
To set your own Location click the Manual location checkbox to ON and Manual night duration to OFF like this
When you set this location Iris will use some complicated math to calculate the sun position and adjust gradually the Color Temperature and Brightness of the screen.
Latitude and Longitude are standard geographic coordinates.
For your city you can find them from site like http://www.latlong.net/ or Google Maps.
From the LatLong site you just enter your city name, click Find and copy the result to Iris like this
So this location thing is useful when you are behind VPN or proxy, but if you want custom night duration you can set Manual night duration to ON and set Manual location to OFF like this
The values for Night start and end time are hour from 0 to 24. So you need to enter a number between 0 and 24 to tell Iris the preferred night duration.
I also plan the add transition duration here and the UI may change a little in the future.