When the association sets up a membership fee, the membership period is fixed. However, a member can start their membership before the fixed start date of the membership fee. The solution here is either to allow the person to join for free during the period leading up to the start of the membership fee, or to offer the member a graduated price, so that the member pays for the exact number of days they are on the membership. Read more about free membership here. Read more about graduated pricing here.