If I needed to be completely unambiguous, I'd say one thing like "should be sent just before ...". Alternatively, sometimes the ambiguity is irrelevant, despite which convention ruled it, if a bottle of milk stated "Best f used by August tenth", you couldn't get me to drink it on https://paxtoncpwix.evawiki.com/9734006/the_2_minute_rule_for_lumber_prices_near_by