You can purchase this file by visiting https://www.sosinvision.com.br/index.php?/file/226-change-post-date/
This resource will allow moderators, with proper permisison, to change the posts date.
Admin CP, -> Members -> Staff -> Moderators. Edit moderators you want -> enable the Can change post date? permission.
Be careful when changing date from a post. You can have issues when merging/splitting posts if you set a date and it broke the logical sequence of posts ID of the topic.