A lot of these dates will be very conservative to allow for the sort of cockups in timing for delivery, storage, and the varying conditions which all of this can be done in, as MattH alluded to earlier in the thread
That probably means that for a lot of stuff you can happily eat it some time after it's best before/use by date has expired, but of course you don't know exactly how the food has been handled, so you could be unlucky, and eat something which is actually past it's actual safe to consume date.
Of course, people also vary in the ability to deal with bugs in the food. No food is entirely 100% clear of nasties, but our bodies are pretty good at dealing with the bugs, and the poisons which they put in the food. Some people are likely to be more prone to suffering from this (eg the young, the old, and the infirm), so presumably the dates also have to allow for this, and are specified in terms of those in our society who are most likely to suffer (obviously excluding people who have medical conditions which may make them unusually extremely sensitive).
I'm not sure that answers the original question, but four days over their date, at this time of year (when if left badly stored in the back of a truck, or at the supermarket, it won't have suffered as badly as it would have in the middle of the summer), I would have been inclined not to worry too much, so long as the method of cooking was going to ensure a high temperature throughout the meat.