Warning: this hint only applies to very old Mac systems!
To turn menu clock off (whether it is "Superclock" or the one built-in to System 7.5) hold down the option key and click on the clock display. To turn it back on again just option-click where the clock would normally be.
My latest blog post: Think for Yourself: In the end, everything is just an opinion. Be skeptical, and think for yourself! (posted 2026-04-25).