automatic unattended macOS update?

[The title of this post is somewhat more general than the problem at hand, because a general solution, if any, would be useful in other situations.] There is an update to macOS itself (Ventura 13.3) but I want to do it after Time Machine finishes the current backup. But, Time Machine says that it will take 18 hours. How can I ask the OS to update itself, unattended, after Time Machine finishes **or** after 24 hours, say. Or, would the updater wait for Time Machine to finish? (I don't want to try.) I don't mind using the command line tool softwareupdate: I could just say sleep $((24*60*60)) && sudo softwareupdate -r, but I don't know how to supply my password to the updater.