Tasks can be set for a future date to activate. When set for a date in the future, the task will NOT show up as Active until the date arrives and therefore is "inactive" until said date. Setting a future date on tasks is a good way to create reminders of things that need to be done in the future.
Keep in mind however, that because individuals are able set future dates it is very important to have a task view for these future tasks that can be monitored by more than one person. Doing this prevents the possibility of dropping the ball on a future task that was created by an individual who no longer works for the company.