Most of the time Apple’s stuff just works behind the scenes. We perform the tasks we need to do on our Macs without thinking about the System underpinnings. One of those “underpinnings” is called Security Certificates. You need updated, current Certificates to install versions of macOS and other software for example. It appears that many of these Certificates are expiring on Oct. 24, 2019. Apple is working furiously to update all these Certificates to avoid any user problems, but this information is a little disconcerting to say the least. This article describes how this happened and what Apple is doing to correct it.