If you don't mind paying a few bucks, I highly recommend Tasker. This automation utility allows you to set up many built-in (and some 3rd-party app) Android actions based on various parameters, including time of day.
In Tasker you will need to create 2 separate profiles, and to each add 2 actions. 1st action will be identical in both profiles - disabling the Auto Brightness. Second one will be similar - a time-based action to change the display brightness, with time of day and brightness level being the differences.
- Start Tasker and tap the
+ button on the bottom o the main screen to create a new profile. Give it a descriptive name, such as "Brightness Down" for example.
- Choose the "Time" context on the presented menu.
- For the "From:" option select the time of day you wish to have brightness lowered.
- Un-check the "To:" option, and tap the green "Accept" button.
- On the "Task Selection" dialog tap the "New Task" button and name it "Lower Screen Brightness" and tap the "Accept" button.
- Tap the "+" button to add an action, select "Display" category, select the "Auto Brightness" action, select the "Off" option on the "Set" drop-down, and press the green "Accept" button.
- Tap the "+" button to add another action, select "Display" category, elect the "Display Brightness" action, set the desirable low level (20 being the lowest recommended setting), ensure that both "Ignore Current Level" and "Immediate Effect" options are checked, and tap the green "Accept" button.
- Tap the green "Accept" button on the "Task Edit / ..." screen.
- On the main screen tap the "Brightness Down" profile once, then tap on its wrench button, and select the "Clone" option.
- Tap the newly-cloned profile, tap its wrench button, select the "Rename" option and name it "Brightness Up".
- Tap on the clock icon, select the "Edit" option, change the "From:" time to the time of day when you'd like brightness increased, and tap the green "Accept" button.
- Now tap on the task itself (name you gave it in step 5), select "Rename" option, name it "Increase Screen Brightness", and tap the green "Accept" button.
- Tap the task again, and select the "Edit" option.
- Tap on the "Display Brightness" action, set the Level to a higher setting, and tap the green "Accept" button.
- Tap the green "Accept" button on the "Task Edit / ..." screen.
- Ensure that on the main screen, the button on bottom-right reads "On", and exit the Tasker app.
You should now be all set.