I am required to submit a certain form "within 30 days of [a certain date in the future]". I suspect that the form's author actually meant to say something like "at least 30 days before [a certain date]". However, a literal reading of the statement would suggest that the form must be submitted "sometime during the 30 days before or after [a certain date]". In context, is that a correct (or at least reasonable) interpretation of the statement? Alternatively, is there perhaps some idiomatic meaning of the phrase "within x days of" that I am not aware of?
Please do not mark this question as a duplicate. I know that vaguely similar questions have been answered, but they do not quite address this specific issue.
Thank you in advance for your help!