Back when Apple first released iOS 9.3, the company introduced a feature called "Night Shift". This feature is essentially Apple’s own take of F.lux, a screen colour temperature control application that reduces blue light generated by the monitor in order to combat eye-strain.
This feature will no longer be iOS exclusive as the MacOS Sierra 10.12.4 beta shows that Night Shift will also be made available for any Mac that runs on Sierra. For those who do not have access to the 10.12.4 beta, the final version of the update is expected to be made available alongside iOS 10.3 which has a March-April release window.
Should you find Night Shift to be lacking, you can always fall back to the tried and tested F.lux application.