I think that the date thing is a bit of a red herring - well it was for me.
From your home screen if you double click your home button you get a list of apps across the bottom. Hold your finger down on one of the apps until they start shivering and little red no-entry circles appear in the top left corner of each of the apps listed. Go to the app store logo in this list and press the red circle to properly close it.
Press the home button again to get back to the home screen. Reopen the app store again.
It worked for me - but not the kind of basic problem you would expect from our friends at Apple.
Or maybe of later, it is...