Neither Mate nor XFCE offer any native means of changing the theme based on the time of day (Sunrise, Sunset, etc). Nevertheless, that hasn't stopped people like the Zorin OS Team from porting their own "Appearance" app to XFCE, and with it the option to schedule Light Mode/Dark Mode.
Other than outright porting that into Linux Mint, one solution might be to incorporate the functionality into this app, seeing as it's designed for both Mate and XFCE, and both are relatively similar in theme options.
Another solutions would be to port the Cinnamon "Dark Mode" applet to the respective Desktop Environments, although this I feel still needs to mature in it's native Desktop Environment first.
Neither Mate nor XFCE offer any native means of changing the theme based on the time of day (Sunrise, Sunset, etc). Nevertheless, that hasn't stopped people like the Zorin OS Team from porting their own "Appearance" app to XFCE, and with it the option to schedule Light Mode/Dark Mode.
Other than outright porting that into Linux Mint, one solution might be to incorporate the functionality into this app, seeing as it's designed for both Mate and XFCE, and both are relatively similar in theme options.
Another solutions would be to port the Cinnamon "Dark Mode" applet to the respective Desktop Environments, although this I feel still needs to mature in it's native Desktop Environment first.