I always go on my machine when it is light, lose track of time, and when I look outside again, it is dark. So I was wondering if there was some sort of app which would change the colour of your screen in a very gradual way to show you the day going by? Just so that the screen's shade slightly changes. I am running Ubuntu GNOME 15.10 with GNOME 3.18. Also I would prefer this to be something that I can install from the repositories so that I can definitely trust it.
Redshift is the app just for you then! Install it with:
sudo apt-get install redshift-gtk
And then run it with the same package name.
Though you will have to turn location services on by going
System Settings > Privacy and then turning them on if they are not already on (this should be roughly in the same place on other flavours):
Adjusts the color temperature of your screen with GTK+ integration The color temperature is set according to the position of the sun. A different color temperature is set during night and daytime. During twilight and early morning, the color temperature transitions smoothly from night to daytime temperature to allow your eyes to slowly adapt.
To configure it to autostart just launch it and then turn on
Autostart in its appindicator menu:
I am sorry that I cannot provide screenshots for comparison as the shading does not affect the screenshots, which is probably for the best.