How to change the date on which a user was created? I'm creating users on my new website that were active on my previous website and I'd like to point this out on there profile pages by displaying the correct date in the "Active since" field.

Is there a possibility to change the user-creation date?
Here's a link to expose the creation date for drupal 6 - someone more knowledgeable with the conversion might be able to help you change it over to 7.
Otherwise, if there are not too many users, you could do it manually via database manipulation.

https://drupal.org/node/857846