I wasn't terribly happy with this either. The cert exists, otherwise we wouldn't be here. It's possible it's corrupted, but I wavered back and forth on whether or not I care at this point. If this is called, the certificate wasn't accepted so they have to re-login anyway. It's only use is to make the message to the user look a bit prettier by telling them "Your stuff expired last week." as compared to "Your stuff is expired." So it's a weak best-effort approach (more of a give-it-a-shot approach); if we get a date, cool, if not, no biggie.

From a code standpoint, what I just described is a lot of preconditions to both the calling of this method and expectations on its results that aren't documented. At very least I need to justify this decision with comments.