my main machine is a MacPRO black trashcan. and until today I was running High Sierra (10.13.x). and I really like that version of macOS. but today I upgraded to Mojave (10.14.x). and that was a Charlie Foxtrot.
I started playing with Visual Studio for MAC and Visual Studio. Using the Xamarin part of it allows me to write mobile apps for both iOS and Android. VS2019 requires XCode 11.1 (or later) on the macOS. XCode 11.1 requires Mojave (or newer). hence why I gave up High Sierra for Mojave.
the installer for Mojave has an expired cert within it and it wont install. I downloaded it several times and even got a copy from a fellow developer to make sure it wasnt just me. so I changed my machine’s clock to be a year ago (2018) and all a sudden the installer works like a champ. the only reason I had a clue about the clock was a fellow developer mentioned he heard there was some issue with expired certs.
if it was for my circle of friends, I would be still bashing my head on the wall on why the O/S wouldnt install.