the certificate wouldn't have expired as a precautionary measure.
all certificates have a valid time on them.
so for example go to https://www.microsoft.com
and click on the padlock and click more information.
in the more information screen select view certificate.
the click on the details tab.
you'll see a heirachy
Baltimore cyber trust root (this is trusted by your computer by default, when you install trusted root updates from windows updates it alters what root authorities it trusts. (sometimes saying, they were crap at that and issued bad certs, don't trust them!) and sometimes issuing new certificate roots as new players enter the game. -certificate roots are also sometimes removed if the private keys are leaked, because then anyone could generate certificates using the certificate authorities private signing key.
you see that microsoft bought their certificate from MSIT Machine Auth CA2.
we don't know who they are, all we care is that they are trusted enough to be given a signing certificate from the company Microsoft internet authority.
and they were trusted enough to be given the certificate from Baltimore Cyber Trust root...
the pane just below that has certificate fields.
if you clisk on subject it'll say CN (common name) = Microsoft Corporation
so if this certificate ends up on google.com then you know something is wrong and you don't trust it.
you'll also see a field marked validity,
with not before 12/01/2013 -meaning that whilst they certificate might have been uploaded to the web servers is won't be able to be used until after this date.
and a second field called not after 12/01/2015 this means that after this time that certificate won't be able to be used.
And it would throw up the error that you see there. unless of course someone pays more money to renew that certificate before it expires and uploads the new certificate.
Basically, the company needs a new cert. you could be friendly and politely point this out to them.