You can use an app to do this as well. f.lux was the first app in this category I think and is still a great choice. I run it on a Macbook. There are similar

You can use an app to do this as well. f.lux was the first app in this category I think and is still a great choice. I run it on a Macbook. There are similar apps for phones as well. Some phones now include built-in functionality to do this as well.