Out of date chocolate is perfectly safe to eat although it just becomes less tasty when it gets out of date and the texture changes as well.
You can eat the out of date chocolate if you want to eat it or you can use it for cooking with where the stale taste of the out of date chocolate won't be noticeable.
You can keep chocolate fresher by wrapping it in plastic and refrigerating the chocolate but for best taste eat the chocolate before expiration date.
However you will be just fine if you do eat the out of date chocolate as I've eaten out of date chocolate many times before without getting sick.