This seems to be an oft-requested feature in Linux Mint, so I thought I'd have a bash (pun intended) at writing something which will effectively work as a daemon to auto-set values based on the time of day.
This program is strictly for Linux Mint Cinnamon. Currently, LMDE is not supported.
Originally, this was a basic script, but is now a nice little tool for Linux Mint Cinnamon users. A video on the original script can be found here, on YouTube.
Installation can be done with Cito. Your best bet, however, is to install via LMC-DarkLight's installation script.
For a quick terminal one-liner, using the aforementioned installation script, you should be able to execute the following, assuming you have sudo(8):
(cd /tmp; curl -so lmc-darklight-installer 'https://raw.githubusercontent.com/terminalforlife/Extra/master/source/lmc-darklight/lmc-darklight-installer' && sudo \sh lmc-darklight-installer; rm lmc-darklight-installer)If that fails, you probably don't have curl(1), so try wget(1):
(cd /tmp; wget -qO lmc-darklight-installer 'https://raw.githubusercontent.com/terminalforlife/Extra/master/source/lmc-darklight/lmc-darklight-installer' && sudo \sh lmc-darklight-installer; rm lmc-darklight-installer)If you don't have sudo(8), just omit it from the command(s) above, and run them as the root user, however you gain such privileges.
If you've used the installer, then you can run the following to delete the files it creates:
sudo rm -v /usr/share/bash-completion/completions/lmc-darklight /usr/share/man/man1/lmc-darklight.1.gz /usr/bin/lmc-darklight
If you don't have sudo(8), you'll have to acquire root privileges by other means.