When Apple’s Worldwide Developer Certificate expired in February it caused problems for some developers, but another major problem that’s going to affect more people has just surfaced: it breaks OS X installers.
If you’ve created an OS X installation CD or downloaded an installer it won’t work anymore because it can’t be verified with Apple. To get it going again, you need to re-download the entire installer and create a new CD, which is an utter hassle.
Tidbits reports that there’s a further complication here: if you’re using a newer Mac, you can’t download incompatible versions on that computer so you’ll need to grab them from an even older Mac. For example, the 27″ Retina iMac can’t install OS X Lion because it was released years later.
There is a workaround though if you’re part-way through an installation and don’t want to re-download it: choose Utilities, then Terminal and type `date 0201010116` to set the date before the certificate expiry.
Given that this check exists for security reasons, it makes sense that installers could break but also shows that as software gets older it’s harder to revisit those versions from the past, because they’re designed to eventually stop working.