If I wished to be entirely unambiguous, I'd say something like "have to be sent in advance of ...". On the other hand, in some cases the ambiguity is irrelevant, it doesn't matter which Conference ruled it, if a bottle of milk stated "Best f used by August 10th", https://premiumlumbersforsale85172.birderswiki.com/1603524/5_easy_facts_about_used_lumber_for_sale_described