Hello. Purpose of Date Published?

When I schedule a submission for an issue that is already published, the submission will be published immediately, no matter which date I choose in the box below (“published”) and if the issue is unpublished the date doesn’t have any effect as well and is not visible to anyone but the editors that look it up where it was entered. Did I miss something? What is it for?

as i know this date is not for schedule for publish, its the only the article publish date which appear in the article page.