I need this because i migrated my community from vBulletin to Discourse but i was not able to migrate the registration dates so i want to do this manually now for each user that makes a request.
I believe this is an easy job for a experienced programmer so i can offer $50 to $100 for this task.
I don’t think a plugin is needed for this. I do not know the insides of Discourse, but an SQL command will do what you are asking. Hoping someone provides more information for you, but it should be a rather trivial task.
The vbulletin script imports created_at. Was something wrong with the database? Do you have all of the dates somewhere? Like @David_Collantes said, fixing all of the dates is probably a better solution than creating a plugin to let you do it by hand.