If a court rule says you have 30 days to answer a paper that was *mailed* to you, how many extra days do you typically add when marking your calendar?

When a court rule provides 30 days to answer a paper that was mailed to you, you typically add 3 extra days when marking your calendar. This additional time is a standard procedural rule, often found in Federal Rule of Civil Procedure (FRCP) 6(d) and mirrored in many state rules of civil procedure. The purpose of adding these 3 days is....