Iris is a simple application which automatically varies your display brightness and colour temperature according to the time of day, with the aim of reducing eye strain.

The program does this entirely automatically. Just launch Iris and it detects your location, adjusts display settings and updates them over time.

If this causes any problems, a system tray menu has right-click options to pause the effect or close the program entirely. (Iris doesn't install any drivers, services or other low-level components, so closing it down will return your system to normal immediately.)

Is Iris any better than the host of similar tools? The developer says:

Some of the benefits of Iris over competitors are that Iris works even on docking stations and monitors connected with USB with the help of my custom High level Color-API, it has really bigger blue light reduction color range compared to all other alternatives, brightness without pulse-width modulation, manual settings, color effects, font rendering, magnification and part screen blue light reduction with the help of full screen overlays.

The Free version gives you only the most basic functionality, but if you're interested in this topic, spending $10 on a lifetime licence to the Pro build does deliver a lot more:

 - Iris high and low-level Color APIs
 - Preserves perfect display calibration during the day
 - Temperature slider
 - Brightness slider
 - Manual/Automatic Temperature
 - Manual/Automatic Brightness
 - Manual/Automatic Location
 - Manual Night duration
 - Keyboard shortcuts
 - Multiple monitors option support
 - Pause color changes when this software is running
 - Everything in Iris lite
 - Multiple Color temperature schemes - Magmus, Olaf, Iris
 - Color inversion and color effects
 - GDIPP, ClearType and other font renderings
 - Break reminding and timers
 - Part screen color changing
 - Block webistes and applications
 - Magnification
 - AI
 - Blink detection
 - Exercises
 - Automatic updates
 - Hidden features
 - New features and innovations