@Graeme: I do understand that this is a frustrating issue for you, but please help us to help you by posting a new thread – as previously advised. I do appreciate it represents a notable problem in terms of calendar functionality, but then again we don’t actually know at this point that there is a bug in our code (in Andy’s case, for instance, this was triggered by his theme – Dandelion – which essentially veered from normal practices).
@John: similarly, if you know that your theme is already making the correct use of the body_class() function then it’s highly likely that the problem is quite different in your case, even if it has similar symptoms. Please do create a new thread and one of the team will be only too happy to help.
Andy: how are you getting on – can you confirm if the suggestion I made worked in your case?