When I recieve a submission, I go and check to be sure the participant has 50 posts. The rules haven't changed. In reality, there would be no way to know how many posts someone had at the time the calendar contest started. The count is always moving as you post. So....the rule is when you submit, I check. If you have at least 50 and a picture that meets the size requirements....you're in.
Keep on posting sbird. You haven't made one bad post yet.