Monthly site rental periods question

Been in parks that, for a monthly rate, have time start on the first and end on the 30th - you don't get the 31st included however if the month is Feb, you only get 28 days or, once every 4 yrs - 29 days. Other parks (most I've been to) give 30 days from date of check in. Doubt there is a 'standard' and even if there were, the park you might be interested in may not adhere to 'standard.' Pick the park you are most interested in, figure out your start and end date and call the park to make a reservation from x date to y date for the monthly rate of z. They'll either accept the reservation or not without getting into complicated questions with someone who may or may not understand your issue.